The post–World War II period marked a turning point for aviation law. From 1947 onward, with the Chicago Convention entering into force, international civil aviation began to operate under a shared legal framework designed to support air transport that is safe, orderly, and fair. From that moment on, international treaties became the main instrument for harmonizing rules among States and providing a common legal basis for international air operations.
One thing mattered above all: continuity. The transition from a provisional structure to a permanent one was not treated as a technical detail, but as a strategic goal. As Mackenzie (2010) puts it, “maintaining continuity between the provisional organization and the permanent one was an end in itself.” In practice, this meant building the new system without losing the institutional experience that had been accumulated before the war.
This is where Albert Roper (1891–1969) becomes especially relevant. A French jurist and former Secretary General of the International Commission for Air Navigation (ICAN), Roper played a key role in carrying that continuity forward. He served as the first Secretary General of the Provisional International Civil Aviation Organization (PICAO) and later of ICAO. His leadership helped ensure that the shift from earlier mechanisms to a permanent global structure was not a rupture, but a controlled and coherent evolution. The goal was clear: preserve institutional knowledge, strengthen cooperation among States, and maintain legal stability in the new international aviation order.
From the 1950s onward, international aviation law did not simply grow, it became more specialized. Through conventions, protocols, and amendments developed within ICAO’s framework, States responded to major challenges: rising air traffic, rapid technological change, protection of third parties on the ground, operational safety, and eventually environmental concerns. Over time, this produced a tightly interconnected legal system in which international cooperation was no longer optional, but essential.
To appreciate the role these instruments played, it helps to define what a treaty is in international law. A treaty is a formal and legally binding agreement between two or more States (or other subjects of international law) intended to create mutual obligations. It may be called a convention, agreement, protocol, or pact, but the legal nature is the same. Typically, it involves negotiation, signature, and ratification, and once in force, States are expected to comply in good faith. In aviation, treaties are among the primary sources of law because they establish shared rules across jurisdictions. They are also supported by other sources such as international custom (including the principle of State sovereignty over its airspace), jurisprudence, and specialized doctrine.
With that foundation in place, international aviation law was built through a series of treaties that shaped modern civil aviation in practical terms. Early on, the Geneva Convention (1948) strengthened legal certainty by addressing international recognition of rights in aircraft, including ownership, leasing, and security interests, an important step for investment and economic development in the sector.
Soon after, the Rome Convention (1952) introduced uniform rules on damage caused to third parties on the surface by foreign aircraft, including liability limits and standardized compensation criteria. These limits were later revised, most notably through the Montreal Protocol (1978), to reflect changing economic conditions. In the same modernization trend, the Hague Protocol (1955) amended the Warsaw Convention (1929), raising compensation limits and simplifying documentation as commercial air transport expanded rapidly.
By the 1960s and 1970s, another issue moved to the forefront: unlawful acts in aviation. The Tokyo Convention (1963) established shared legal principles for criminal jurisdiction on board aircraft and recognized the aircraft commander’s authority to preserve safety and order in flight. Later, the Hague Convention (1970) classified unlawful seizure of aircraft as an international crime and required States to cooperate through jurisdiction, extradition, and prosecution. The Montreal Convention (1971) expanded the legal framework further, addressing additional acts against the safety of civil aviation.
At the same time, aviation law began to feel the pressure of economic change. The Montreal Air Transport Conference (1978) reflected a shift toward liberalized markets, strongly influenced by the U.S. Airline Deregulation Act (1978) and its wider international impact. As the regulatory landscape changed, ICAO took on a more active role, trying to balance market liberalization with operational safety and fairness among States.
Taken together, the years 1947–1980 represent a clear consolidation phase in international aviation law. Treaties did more than formalize rules. They reinforced a basic truth: international aviation can only function through sustained, practical, and effective legal cooperation.