The markings of military aircraft under the law of aerial warfare

The breakthrough innovation of the Wright brothers in 1903 and subsequent developments of aerial technology created significant opportunities for the military, as a new dimension of warfare became an operational space of combat. Many legal questions arise, including the status of air machines deployed by the freshly formed independent air detachments before the outbreak of World War I. From the operational and legal viewpoint, both state practice and international law experts agreed that in order to receive a status similar to warships under the law of naval warfare, military aircraft should bear distinctive insignia, indicating their military character and nationality. This article’s aim is to present the origins and evolution of the military markings and their legal significance, as a core element of the military aircraft definition. It needs to be emphasized that only aircraft considered as military can perform acts of hostility and exercise the specific rights granted by the law of air warfare. The analysis will refer to practical challenges for maintaining the classical rule of air warfare, such as the exact location of the markings on the aircraft surfaces, low-visibility insignia (as a way to reconcile legal and operational demands) and the question of relevance of the duty to mark military aircraft in the context of unmanned air platforms. Militärflugzeugen darzustellen. Es muss darauf hingewiesen werden, dass nur Flugzeuge, die als militärisch angesehen werden, feindliche Handlungen durch-führen und die durch das Gesetz der Luftkriegsführung gewährten spezifischen Rechte ausüben können. Die Analyse wird sich auf praktische Herausforderungen für die Aufrech-terhaltung des klassischen Gesetzes der Luftkriegsführung beziehen, wie die genaue Lage der Kennzeichen auf den Flugzeugoberflächen, Kennzeichen mit geringer Sichtbarkeit (als Mittel, rechtliche und operative Anforderungen miteinander in Einklang zu bringen) und die Frage der Relevanz der Pflicht zur Kennzeichnung militärischer Flugzeuge im Zusammenhang mit unbemannten Luftplattformen.

La revolucionaria innovación de los hermanos Wright en 1903 y subsiguiente evolución de la tecnología aérea dieron paso a oportunidades significativas para los ejércitos, creándose una nueva dimensión de la guerra que se convirtió en un espacio operativo de combate. Esto trajo consigo muchas cuestiones legales, incluido el estatus de los artefactos aéreos desplegados por los recién creados destacamentos aéreos independientes en los prolegómenos de la Primera Guerra Mundial. Desde el punto de vista operativo y legal, tanto los Estados a través de la práctica como los expertos en Derecho Internacional estuvieron de acuerdo en que para acogerse al mismo estatus que los buques de guerra bajo las leyes de la guerra naval, las aeronaves militares debían llevar insignias distintivas, mostrando su carácter militar y nacionalidad. El propósito del artículo es examinar el origen y evolución de estas señales militares y su importancia legal como uno de los elementos principales de la definición de aeronave militar. Debe enfatizarse que solo una aeronave considerada militar puede llevar a cabo actos de hostilidad y ejercer derechos específicos reconocidos por las leyes de la guerra aérea. El análisis aborda los retos prácticos para mantener la vigencia de la regla clásica de la guerra aérea, tal como es el lugar exacto de emplazamiento de las señales exteriores en la superficie de las aeronaves, las insignias de baja visibilidad (como una forma de conciliar las exigencias legales y operativas) y la cuestión de la relevancia del deber de señalar las aeronaves militares en el contexto de las plataformas aéreas no tripuladas. The arrival of military aviation, as a new part of the armed forces, highlighted the issue of aircraft identification. Aside from operational difficulties, such as 'friend or foe' identification in combat, the nineteenth century doctrine of international law struggled to form an acceptable legal framework for air operations in the context of an armed conflict. There was a general understanding that the air warfare regime should entail similar solutions as sea warfare and as a supportive source of obligations -the law of land warfare. The status of military aircraft was compared to that of warships, and it was agreed that in order to exercise the belligerent rights, both type of vessels should distinguish themselves from other objects. This led the French jurist Paul Fauchille to the conclusion that military aircraft should bear a distinctive and visible mark of their nationality. Therefore, the state swiftly adopted the proposal, even before the outbreak of World War I. The aim of the article is to present the historical development of both state practice and specific legal obligation regulating the scheme of aircraft markings. This article provides examples of inconsistent types of insignia and analyses the changing nature of the definition of military aircraft. In addition, the article discusses the practice of using so-called 'low visibility' insignia and the problematic issue of unnamed aircraft status.

HISTORICAL BACKGROUND
The emergence of a characteristic emblem painted on military aircraft surfaces is intertwined with the first regular air services operating within the military structures of states armed forces. In 1909, the French constructor Louis Bleroit developed the novel concept of the Wright brothers plane, and its showpiece air-frame 'Bleroit XI' successfully crossed the English Channel, astonishing military experts. 1 As a result, the French government decided to launch a training programme for future pilots and conducted a series of experimental tests for the possible adoption of civilian aircraft for combat services. Quickly overcoming the scepticism from senior high ranking officers, France was the first country to establish a permanent structure of military aviation. The breakthrough date in this case was 29 March 1912, when the French Parliament adopted the Bill creating French military aviation. 2 On 26 July 1912, the new amendment passed, with an order to paint any French military aircraft with the specified and distinctive three-colour roundel. 3 Simultaneously, the same pattern of military aircraft introduction could be observed among other European Powers. Germany, in 1913, formed their air force detachment (Luftstreitkräfte), which adopted the symbol of German highest military decoration -the Iron Cross (Eiserne Kreuz) 4as its marking. Under the order of the German Air Force Inspectorate in the second half of 1918, all aircraft manufacturers were obliged to paint their airframes with a new type of emblem -Balkenkreuz, which was later deployed by the Hitler's Luftwaffe during World War II. 5 On 11 December 1914, the Royal Flying Corps decided to imitate the French type of markings and adopted the roundel but 'with the colors reversed, that is with a red circle inside a blue ring'. 6 Furthermore, British air force insignia was subjected to various transformations between 1915 and 1970. While the core of emblem remains unchanged (blue ring around red core), there were multiple modifications of the markings -for example, the adoption of the 'night' insignia and the use of the extra colour pallet (white and yellow to improve identification and differentiate from the French signs). 7 For instance, during the Battle of Britain, the Royal Air Force (RAF) aircraft displayed three different types of symbols. The uniqueness of RAF markings is the presence of an additional painting located on the rudder (fin-flash).
A similar transformation could be observed in the US' military aviation. While the distinctive 'White Star' has been displayed in all types of deployed insignia (with the exception of the American Expeditionary Forces activity at the European theatre in 1917-18, where in order to maintain Allied types of marking, the US aviation used the tricolour roundel), the specific composition of the markings evolved during that stage of history. 8 After World War I, the US military aircraft displayed the roundel-type insignia with the 'White Star' inside the blue circle and a red dot in the centre. 9 Experience gained by the US aircrews during combats with Japanese aviation underlined the need for a new marking shape. In 1943, the distinctive stripes were added to the 'White Star' symbol, and, since 1947 this type of insignia has been displayed by all military aircraft of the US Air Forces (National Star Insignia). 10 The Japanese national roundel (hinomaru -'Sun disk') remains in use and unchanged since the establishment of the first Japan air force detachment in 1912 and its successor the Japan Air Self-Defense Air Force in 1954. Also, the Imperial Russian  on the current legal framework of aerial domain with the draft of the regulation. 13 Article 2 of Fauchille's draft of 1902 stipulated that 'public (military included) or private aircraft should present external markings' which would allow for swift visual identification of the nationality of the aircraft. 14 The French jurist underlined that a 'stateless' aircraft could be compared to pirate vessels and treated accordingly, as in the law of the sea. 15 He excluded the possibility of allowing military aircraft to operate under a false flag, pointing out the differences between air and naval warfare. 16 At same session, Fauchille asserted that international law concerning the use of aviation should be comprehensive, addressing both times of peace and war. 17 As a consequence, during the session of the International Law Institute in 1911, he proposed a complete code of the law of aerial warfare. 18 Article 2 of the 1911 draft underlined that only military aircraft are entitled to exercise belligerent rights. It was firmly highlighted that the aircraft need to carry 'clearly distinctive and visible markings'. 19 The participants of the discussion invoked in this place that the potential penalty for failure to comply with Article 2 of the draft will be the denial of the combatant status of the crew. 20 It should be emphasized that the French jurist was not the only legal researcher examining the relationship between the international law and the law of aerial warfare. Another 19. 'Sont considérés comme belligérants, sousréserve de ce qui est dit à l'article 3, les aérostats militaires, c'est-à-dire affectés par l'Etat à un service militaire et placés sous le commandement d'un officier en uniforme de l'armée, de terre ou de mer. Tous aérostats militaires doivent porter, attaché d'une manière visible à leur enveloppe, un signé distinctif de leur Caractère.' Ibid at 28. 20. Ibid at 65. requirement in his own draft (Article 7). 21 Further and more detailed studies on this subject were undertaken by James Spaight, British lawyer and military pilot. Spaight's conclusions and observations are especially significant due to his first-hand experience gained as an aviator. In his research, he categorically underlined the value of the principle of distinction, highlighting that its status must be considered as 'necessary' in air warfare. Spaight might be credited with the formulation of the definition of military aircraft, which stipulates that the aircraft shall: (1) operate under the military jurisdiction, (2) display the visible national insignia, and (3) be manned by air crew subjected to military discipline and respecting the laws of war. 22 With only minimal additions, the definition of the military aircraft proposed by Spaight was at large followed by the Hague Rules of Air Warfare of 1923 (HRAW). 23 The validity of the rule was repeated in the state's expert manuals (San Remo Manual of 1994 and HPCR Air and Missile Warfare Manual of 2009). 24 It might be stated without much controversy that between 1912 and 1914 a norm of customary character emerged, which imposed a duty on states to apply the national military markings on the outer surfaces of all aircraft. 25 As observed in the examples above, the practice in that particular subject was universal, as every state forming its own air force detachment adopted its own scheme of insignia. 26 The subjective element of customary international lawopinio iuris -might be at first a little ambiguous to decode. 27 In hindsight, the states were rather guided by the operational necessities that were driven by the legal undertaking. The priority was visual identification, which allow aviators and other personnel to verify the nationality of the approaching aircraft. 28 On the other hand, the states started to associate this practice with the legal requirement, emerging from the overall duty of every belligerent to properly distinguish members of the military forces and warships. 29 The matter with regard to naval and land warfare was already codified by the VII Hague Convention of 1907 (Article 1) and Hague Regulation of 1907 Concerning Laws and Customs in Land Warfare (Article 1). Presentation of the emblems, flags or insignia indicating nationality became an agreed standard in general international law of war at the beginning of the twentieth century. 30 Moreover, the strict definition of the warship in the regime of naval warfare could be attributed to the whole range of rights which might be exercised exclusively by them, the question of immunity included. 31 In fact, the immaterial object became the subject of specific legal provisions. 32 The 'personification' of the warships was a gateway to accepting a similar analogy in the context of the military aircraft. 33 The conduct of World War I fully confirmed that the duty to mark military aircraft is a part of customary international law. 34  were considered uncontroversial and a reflection of the de lege lata. 37 Article 3 of the HRAW underlined that the status of the air vessels should be evaluated by an 'external mark indicating its nation and military character'. 38 The provision entails a novelty in the additional requirement for the marking, which should not only indicate its nationality but also 'military character'. However, this amendment should be considered only a technical addition: the practice of the belligerents during World War I clearly confirmed that military aircraft bear markings which are clearly attributable to the air forces, although they are not an exact presentation of the national flag or coat of arms. 39 They are rather an exemplification of the national colours or very distinctive symbol of the state: for example White Star for the US or the Three-Crown insignia of the Swedish Royal House. This practice was widely observed during the time of drafting of the HRAW and was generally followed by the newly formed air forces after 1945, 1960 and 1991. 40 The penalty for not fulfilling the conditions listed in Article 3 of the HRAW is the loss of 'military aircraft' status. Thus, an aircraft which failed to meet the abovementioned requirements would not be entitled to act as a legitimate 'war engine'. 41 In case of capture, the status of the crew would be equal to a civilian taking a direct part in hostilities. The practice of World War I and World War II confirmed the prohibition of the use of false or neutral marks as a legitimate ruse of war (even if the aircraft is used in naval service). 42 Both sides of the conflict captured several pieces of the enemy's equipment painted in national markings, which was later removed and repainted. 43 37. 'Some of these rules were a statement of existing practice, e.g., a military aircraft shall bear an external mark indicating its nationality and military character, and such marks shall be so affixed that they cannot be altered would be sufficient to maintain the 'military status' of the aircraft. On the other hand, according to the San Remo Manual (Article 13(j)), the constitutive element of 'military aircraft' definition is 'having the military marks' (plural). 65 This requirement is confirmed by the wording of rule 1(x) of the HPCR Air and Missile Warfare Manual ('bearing the military markings of that state'). As we observed, the practice of states varies. Also, the new aviation designs make it sometimes impossible to place the insignia on all surfaces (e.g. for aircraft based on the 'delta wings' concept, where the classical fuselage is not present). It seems that the irregular location of markings, or lack of insignia on some surfaces of the military aircraft, have become an acceptable variety of the rule, embodied within the customary law of air warfare.

LOW-VISIBILITY MARKINGS
At the beginning of air warfare, the requirement of visibility, which enabled rapid identification of 'friend or foe', was more important than 'stealth' capacity (see the example of the famous Foker Dr.I 'The Red Baron'). 66 During the late stages of World War II, the German Luftwaffe introduced an advanced scheme for aircraft camouflage. The differences in operational geographic areas (e.g. African and European theatre) and weather conditions (summer and winter seasons) demanded a more detailed type of painting, which would be more difficult to distinguish from the above. 67 In such circumstances, the Balkenkreuz sign was considered an element compromising the camouflage and endangering the aircraft's survivability. Another reason was the deficit of black paint. To eliminate the bright and illuminating drawings from the surface of the airframe, the German Luftwaffe simplified the insignia colour scheme by removing the black core painting. Before 1939, Polish military aviation, in order to blend the airframe in the sky, painted their PZL P-11 fighters underneath in characteristic 'Polish-blue' camouflage paint. It is worth mentioning that Polish military aviation 'checkerboard' insignia has an intense white-red colour scheme. To reduce its visibility, the insignia placed on the lower side of the wings were applied without the white colour. 68 The experience gained from World War II confirmed that, in some circumstances, the bright and decorative colour scheme of the national air force insignia might be a detrimental element for the aircraft's and the crew's survivability. As time progressed, the development of the radar reduced the need for the visual requirements of the air vessel. 69 Air combat evolved from frontline combat to long-range engagements, where the enemy cruises under the sub-sonic speeds and missile guidance systems are capable of destroying aircraft even hundreds of kilometers away. The latest Russian design anti-aircraft system, S-400, is able to attack and destroy flying objects within a range of 385 km. 70 An updated version of the AIM-120 Raytheon air-to-air missiles has an operational range of 160 km. Nowadays, the determination of the character of the aircraft in contemporary air warfare conditions is solely based on the radar signature. In light of such circumstances, the practical role of the markings (as a method of long-range identification) is marginal. 71 On the other hand, the state still observes the requirements arising from the HRAW of 1923. In order to reconcile the conflict between the practical realities of the battlefield and the legal requirements, many states decided to adopt a new type of insignia (generally referred to as 'low visibility'). The markings are usually repainted in gray-scale (e.g. US) or faded shades of colours (e.g. UK). Prima facie this practice is a violation of Article 13 of HRAW, which demands that the aircraft markings be 'visible'. On the other hand, as observed by M Schmitt, no single state has protested against the employment of low-visibility markings. 72 This harkens back to Wolf Heinstchell von Heineeg's statement that the 'absence of any objection to widespread practice evidences its lawfulness'. 73 The same approach had been accepted by the experts during the drafting of the HPCR Air and Missile Manual, stipulating that '(…) States do not consider this practice to be unlawful'. 74  military potential of unnamed air systems. 78 Nevertheless, it was beyond imagination that such pilotless aircraft would be capable of conduct combat operations, attributable to conventional military aircraft. 79 This impacted the later legal developments relating to the law of air warfare, and, as a consequence, the status of unnamed military aircraft was out of scope of the HRAW drafters. Obviously, this did not mean that pilotless aircraft were developed by the constructors.
The analysis of photographs from the World War II period provides intriguing conclusions. In 1941, during Winston Churchill's visit to the Royal Navy station, the pilotless de Haviland 'Queen Bee' drone was marked accordingly based on the schemes which were binding at the time in the Royal Air Forces. 80 In 1943, the USAAF adopted a programme called 'Aphrodite', whose core principle was to convert obsolete versions of the B-17 Flying Fortress into pilotless, radio-controlled drones with explosives. The bombers displayed the national insignia of the USAAF. 81 A similar pattern was observed in the case of the German Luftwaffe unnamed programme called 'Mistel'. 82 In conclusion, it can be observed that, at least during World War II, the military aircraft operating without crew on board still complied with the requirements characteristic for conventional military aircraft, including visible markings.
During the era of the Cold War, the practice of the states seems much more ambiguous. USAF deploying the 'Firefly' and 'Lightning Bug' reconnaissance drones purposely stripped them of any signs that would indicate their nationality. The actions of those air systems were usually conducted in the grayscale situation of intelligence and covert mission. The Soviet Tu-141 drone's existing airframes showcase the national markings of the USSR. 83 On the other hand, there are reports that during the international armed conflicts which occurred in the 1990s over Iraq, Bosnia and Serbia, USAF 'Predator' drones were deployed without the National Insignia markings. The 'Predator', an unnamed vehicle shot down by the Serbian air defence in 1999 over the Kosovo area and currently on display in Museum of Aviation in Belgrade, bear no signs of national identification. 84 The lack of physical presences of the crew undermines the logic of military aircraft definition. As stated above, the markings served two functions: operational and legal. Operational reasons are contemporarily very limited due to radar technology. In the legal context, the national insignia placed on the aircraft provides multiple rights for the platform itself and grants the combatant status for the operators -as they are parts of the military aircraft definition. Ian Henderson and Bryan Cavanagh suggested that, in that matter the law of air warfare, it is 'moving away from the law of naval warfare and towards the law of ground warfare', where there is no duty to mark military vehicles, considering that the 'customary international law applicable to military aircraft' started to lose 'its military significance'. 85 Despite this remark, William Boothby underlined that if the unmanned aircraft are going to be allowed to perform the act of hostility, they need to fulfill the definition of military aircraft (markings included). 86 From the author's viewpoint, the latter opinion has more legal support behind it. In the existing framework, the definition of military aircraft is, leaving aside the definition of military objective, a rule of paramount importance in law of air warfare. Is it true that the international humanitarian law, especially in the customary law layer, is potent to what the International Military Tribunal described as 'continual adaptation', which 'follows the needs of a changing world'? 87 Nevertheless, the elements of military aircraft definition remain unchanged, despite the differences in technical realities. It might be argued whether the category of 'e-markings' would be a sufficient replacement to the traditional insignia. The authority controlling the airspace (civilian or air defence management) is determining the nationality of the aircraft (manned or unmanned) by their radar signature and identification signs -for example the specific number of flight or special transponder codes. While it seems to be a totally valid argument in the case of civilian traffic control, it is dangerous to believe that the 'e-recognition' of the military aircraft would respect the law of air warfare in the time of armed conflict -especially the principle of distinction and the definition of the military aircraft. For instance, Turkey's latest attempts to acquire Russian S-400 anti-aircraft missiles are meeting with strong opposition from the US. 88 The S-400 platform is not designed to cooperate with the US-made IFF (Identification, Friend or Foe) system, which would pose a great threat to the NATO operations. Without the implementation of the aforementioned system, the anti-aircraft missiles are considering every aircraft and UAV (regardless of the character) as hostile. 89 On the contrary, the negative verification done by the IFF system does not necessarily render the aircraft as a potential 'enemy', but classified it as an 'unknown' object, where additional verification is requested. In fact, this entails the 'old-fashioned' method of visual recognition. Any radio or radar-based identification is also vulnerable to countermeasures or other interference and eventual error might even result in loss of 88. Available at <https://www.reuters.com/article/us-turkey-security-usa/turkey-says-u-soffering-patriot-missiles-if-s-400-not-operated-idUSKBN20X1I8> (accessed 1 October 2020). 89. The IFF system is based on radio-encrypted connection between the transponder and so-called 'interrogator', operating on the restricted sets of frequencies.
life and property -just like the tragic failure to distinguish the Iran Air Flight 655 from the Iranian Air Force F-14 or the 2003 shootdown of the Royal Air Force Tornado by the Patriot system. 90 In consequence, the 'e-markings' or 'electronic identification' is not a sufficiently stable and reliable method of marking military aircrafts, when compared to the traditional requirement. Codes, call signs or radio signals, however useful and overwhelmingly dominant factors in air defence identification, cannot replace the 'ultimate role' of the physical insignia. Markings are constant and served as a source of the aircraft nationality and its status, even in cases of shootdown or destruction. 91 Moreover, while the use of improper markings is prohibited and might in some circumstances be tantamount to perfidy, the use of the false IFF signature is a lawful ruse of war. 92 Despite the theoretical alternative means of distinction -as described in the paragraph above, the contemporary practice of states emphasize that unnamed aerial vehicles in military service have visible markings painted. This is confirmed by the photographic evidence of the UAVs operated by the US, 93  South Korea, 104 Australia 105 and Ukraine. 106 The 'especially affected' states are still following the old-fashioned requirement, forged on the battlefield of World War I and elaborated in a document almost 100 years old. 107 Unlike the vehicles in land warfare, military aircraft have 'personification' in air and naval warfare by becoming a subject of legal provisions. 108 From this 'personification' stems sets of concrete rights and immunities: for example the right to search and visit a vessel, 109 the right of hot pursuit, 110 the right of transporting wounded, sick or shipwrecked, 111 immunity against seizure, 112 and the fundamental right to perform acts of hostilities. 113 Is it lawfully possible for military aircraft to perform those functions without being marked? In the author's opinion, the answer is no. Every dimension of warfare develops its own unique method for complying with the principle of distinction, using its dedicated system of identification, which is based on logical circumstances. In the case of land warfare, this means combatants display a 'fixed emblem'. In naval warfare, every warship presents its flag. The law of air warfare asserts that military markings are an essential element of the military aircraft definition. It has to be accepted that the reality of air combat has changed over the course of history, and visual recognition is no longer a primary source of identification. On the other hand, there are no clear reasons which support the idea of abandoning the obligation to mark military aircraft. Modern markings, by their decals, layouts, shapes or colours, do not compromise the camouflage of the aircraft and situations might still occur where the nationality of the aircraft is determined by sight (e.g. the interception of the civilian airliner in the zone of an armed conflict). 114 The concept of combatancy emanates from the overall duty of belligerents to distinguish. 115 Even in the context of cyber warfare, a majority of scholars still accept the classic notions formulated in the 1899 and 1907 Hague Peace Conferences. 116 If one combines the overall duty to present is combined -'fixed emblem', 'flag' and 'military markings' -with the notion of combatant privilege, there are even more factors which appeal to continuation of the old-fashioned practice. 117 The abovementioned conclusion is supported by the operations conducted by other entities existing in international law. The most relevant case is NATO's aviation, including both unnamed and manned platforms, having NATO markings painted on the fuselage. 118 It has to be underlined that the international government organizations (IGO) are subjects of international law. Legal personality is well-established in the case of the United Nations and other IGOs, however their legal 'independence' is limited by the organization's 'purpose' and 'objectives'. 119 In fact, the UN Charter in many provisions refers to the possibility to deploy armed force as an element necessary to conduct the primal objectives of the organization, for example the main responsibility to 'maintain international peace and security', while NATO is a military alliance. 120 It has to be noted that there has been a discussion as to what extent the peace-keeping forces operating under the UN mandate shall be bound by the rules and customs of warfare, while the organization is not a party to international humanitarian law treaties. 121 The starting point was establishing whether the IGO have the capacity to became a 'party to armed conflict' and be mutatis mutandis a subject of the law governing the conduct of armed conflict, including the legal regime concerning air warfare. Since the nineteenth century the institution called as a 'recognition of belligerency' opened a gateway to accept the legal personality within the law of armed platforms need to fulfil all the requirements of the definition of military aircraft, including the duty to bear distinctive markings. As a result, NATO crews will benefit from the 'combatant privilege', rendering from prosecutions over espionage, as underlined by the JAG opinion of 1980. The case of NATO insignia in other evidence of international practice followed by other international law entities, validates the relevance of the markings as the constitutive element of the military aircraft definition, also in the context of unmanned platforms.

CONCLUSION
The law of air warfare is one of the most ambiguous parts of international humanitarian law. Its vagueness emanates from the fact that there is no dedicated treaty which comprehensively regulates all aspects of air warfare. This requires lawyers to extract and decode relevant norms from customary law. 137 The obligation to mark military aircraft with the insignia indicating its military character was one of the legal provisions which emerged with the deployment of aircraft in a combat role. It has been universally accepted by the countries of the world, and during World War I, it achieved legal significance. Largely, the rule has been valid for over a century. From the state practice, it seems that there are two varieties of the norm, both of which seem to be permissible and uncontested. The first is the adoption of low-visibility markings as a compromise between the operational circumstance and legal restrictions. The second is the acceptance of the non-regular placement of the markings (in a nonsymmetrical way, which still fulfills the general obligation. Even breakthrough innovations in military aviation, such as unmanned and autonomous air platforms, have not challenged the validity of the provision embodied in Article 3 HRAW. Although there are those who question the duty to mark pilotless vehicles, the special status of military aircraft should be kept in mind, especially regarding the right to perform acts of hostility. As an integral part of the definition of military aircraft, there is no exception to the duty to properly mark aircraft. airspace and in case of capture is responsible to intern both the crew and the aircraft. In fact, this would limit the geographical sphere of operations to the areas outside neutral jurisdiction (e.g. high seas) and the territory of belligerent states (if the counterpart to the armed conflict is a state