The Chicago Convention and ICAO's 19 Annexes

The Convention on International Civil Aviation, signed in Chicago in 1944 by 52 states, is the founding treaty of modern civil aviation. It established the principle that every state has complete sovereignty over the airspace above its territory, while also creating a framework for international cooperation so aircraft could cross borders safely and predictably.

The Chicago Convention also created the International Civil Aviation Organization (ICAO), a United Nations specialized agency. ICAO's core job is to adopt international Standards and Recommended Practices (SARPs) — detailed technical rules that member states agree to follow or formally declare where they differ.

These SARPs are organized into 19 technical Annexes to the Convention, each covering one area of aviation. Together they form the backbone of how licensing, operations, airworthiness, air traffic services, accident investigation, security, and more are standardized worldwide, so that a pilot's license, an aircraft's certificate, or an accident report means broadly the same thing in any ICAO member state.

Not every rule in every Annex is binding exactly as written — states can file a 'difference' with ICAO if their national regulation diverges, which is why pilots and crew are trained on their own regulator's rules (e.g. EASA, FAA, GCAA) built on top of this shared ICAO foundation, not the Annexes themselves directly.