In IHL, there are four main treaties: (1) The 1949 Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, (2) the 1949 Geneva Convention for the Amelioration of the Condition of Wounded, Sick, and Shipwrecked Members of Armed Forces at Sea, (3) The 1949 Geneva Convention Relative to the Treatment of Prisoners of War, and (4) The 1949 Geneva Convention Relative to the Protection of Civilian Persons in Time of War [1]. If we take a closer look, while land and sea are covered, the sky is missing. This does not resonate with the fact that air power has been a key element in armed conflict since World War II⎯taking the example of the atomic bombings of Hiroshima and Nagasaki and today, we see the use of sophisticated technology of air power like unmanned vehicles or drones on battlefields. We will try to explore possible answers as to why the Skies does not have a stand-alone treaty among the four main IHL treaties. 

Initially, aerial warfare was already seen as an extension of either land or sea warfare rather than a distinct domain [2]. As seen in two rulings by the Greco-German arbitration tribunal (1927–1930) in which it condemned Germany’s aerial bombardment of neutral cities during World War I, applying Hague Convention II of 1899 to the laws and customs of war on land. The Tribunal cited Article 25 (prohibition of the bombardment of undefended towns) and Article 26 (obligation of a prior warning before bombardment). This marked the first instance of applying the principle that weapons producing similar effects should be regulated similarly, reinforcing the analogy between land and aerial bombardment. Another perspective equated air warfare with naval warfare due to similarities between the domains and the extensive function of the air force for naval power over the land in the eyes of many states. This concept persisted during the discussions at the Hague Conference in 1922–1923, where the Commission of Jurists formulated a draft of the Hague Rules of Air Warfare. 

Historically, a treaty on air warfare under humanitarian law was first discussed in the 1920s [3]. At the 12th International Conference in 1925, a draft adapting the 1906 Geneva Convention to aerial warfare was approved and sent to the Swiss Federal Council. However, the Swiss government deprioritized the issue in 1929 due to an already complex revision agenda (Prisoners of War). Medical aircraft became a particular subject that survived the delay and captivated states attention in the 1929 Diplomatic Conference, despite a lack of time for detailed provisions and insufficient expert representation. As a temporary solution, Article 18 was added to the 1929 Geneva Convention, and states were urged to convene a future conference on the matter. The ICRC later submitted a draft adaptation (prepared by MM. Ch. Julliot and P. Des Gouttes) to the 14th International Conference of the Red Cross in 1930, which was approved and scheduled for discussion at the 1940 Diplomatic Conference [4]. However, World War II delayed further negotiations.

After 1945, the ICRC shifted focus to integrating medical aircraft protections into the Geneva Conventions rather than drafting separate air warfare rules, arguing that existing humanitarian principles applied universally [5]. During WWII, medical aircraft protections were rarely enforced, building doubts about expanding the rules on this subject in the 1949 Diplomatic Conference, let alone air warfare in general. The ICRC ultimately concluded that air warfare did not warrant concentrated legal provisions like those developed for naval warfare in 1907. The abandonment of air warfare remained until the preparatory work of the 1977 Additional Protocol I due to limited work, leading to concerns about the feasibility of addressing it [6]. 

In the political lens, the absence of a dedicated treaty on air warfare can largely be attributed to states’ reluctance to impose restrictions on their already well-developed and superior military weapons and tactics [7].  This reflects the broader tension between military necessity and humanitarian considerations that underlies much of international humanitarian law. Additionally, in a practical sense, we know the law will always get behind the technology. Yet, the rapid advancement of aviation technology, in combination with the subject and economic importance of air forces in the armaments industry, makes more challenging to push the agenda [8]. 

In any event, the absence of a stand-alone convention for air warfare does not mean a legal vacuum, not to mention that general rules on conduct of hostilities remain applicable in all domains [9].  We also have the Hague Rules of Air Warfare, Additional Protocol I (AP I) to the Geneva Conventions, and the Manual on International Law Applicable to Air and Missile Warfare (AMW) Manual [10]. However, these legal products still reserved significant gaps in the regulation of aerial hostilities. Additional Protocol I, despite its significant rule in the general applicability of IHL in the air-ground operations, still excludes air-to-air and sea-to-air combat. Meanwhile, albeit both Hague Rules and AMW Manual serve as authoritative restatement of customary international law on air warfare, they are non-binding on their own (Hague rules never formally adopted). Particularly AMW Manual, although it remains a significant reference in understanding IHL in air and missile operations, it has not been updated since 2009 (the commentary was published in 2013) [11]. 

In conclusion, the idea of having an independent treaty on air warfare was not novel in 1949; it had been drafted, postponed and abandoned. The reason being land and naval warfare caught states more attention and air warfare had been overshadowed by the development of those domains in addition to the gap of expertise. This legal vacuum might also be influenced by rapid evolution of aviation technology and defence industry, feeding the state’s reluctance to allow international law to limit their armaments and arsenals. Instead, the priority was allowing soft laws under the blanket of restated customary international law to develop.