The Sovereignty Framework
Every nation holds sovereignty over the airspace above its territory. The Convention on International Civil Aviation, signed December 7, 1944 in Chicago by 52 states and entered into force April 4, 1947, established this principle as the foundation of international aviation law and created the International Civil Aviation Organization (ICAO). As of December 2024, 193 nations — all United Nations members except Liechtenstein — are signatories.
Because each state controls its own airspace, airlines have no inherent right to fly internationally. Commercial air service between two countries requires a treaty — a bilateral air service agreement (BASA) — granting specific traffic rights. Over 3,000 bilateral agreements have been signed and registered with ICAO since the first, the Bermuda Agreement of 1946 between the United States and the United Kingdom.
The Freedoms of the Air
Traffic rights under bilateral agreements are structured around the "freedoms of the air," a framework that originated from the Chicago Convention. The first two freedoms were codified in the International Air Services Transit Agreement (broadly adopted); the third through fifth are standard components of bilateral agreements; and four additional freedoms are recognized in practice.
| Freedom | Right Granted | Example |
|---|---|---|
| 1st | Fly over a foreign country without landing | Canadian airline overflying the US en route to Mexico |
| 2nd | Land for refueling or maintenance without embarking/disembarking traffic | British carrier refueling in Shannon en route to the US |
| 3rd | Carry traffic from one's own country to another | US carrier flying New York to London |
| 4th | Carry traffic from another country to one's own | British carrier flying London to New York |
| 5th | Carry traffic between two foreign countries on a flight originating/ending in one's own | Singapore Airlines flying Singapore–Frankfurt–New York |
| 6th | Carry traffic between two foreign countries via one's own country | Emirates flying Sydney–Dubai–Paris |
| 7th | Carry traffic between two foreign countries without touching one's own | Irish carrier flying Spain to Sweden |
| 8th | Carry traffic within a foreign country (cabotage, continuing to/from home) | Not granted in US bilateral agreements |
| 9th | Carry traffic within a foreign country (stand-alone cabotage) | Not granted in US bilateral agreements |
Third and fourth freedom rights are the baseline of bilateral aviation agreements. Fifth freedom rights are granted selectively and have been a source of contention, as seen in the US–Gulf carrier dispute.
The US Open Skies Policy
The DOT has pursued an "open-skies" policy since 1992, designed to "eliminate government involvement in airline decision-making about routes, capacity, and pricing in international markets". Under Open Skies agreements, airlines from signatory countries can fly any route between the two countries, at any frequency, using any aircraft, and set fares without government approval.
As of March 2026, the DOT's published list of Open Skies agreements in force includes approximately 130 aviation partners. The list includes all 27 EU member states (plus Iceland and Norway under the US-EU agreement), the United Kingdom, Canada, Japan, Australia, India, Brazil, and the UAE, among others.
On May 1, 2001, the United States, Brunei, Chile, New Zealand, and Singapore signed the Multilateral Agreement on the Liberalization of International Air Transportation (MALIAT), a multilateral Open Skies framework that the DOT continues to promote as an accession vehicle for additional partners.
The US-EU Open Skies Agreement
The US-EU Open Skies Agreement, signed in 2007 and effective March 30, 2008, replaced the patchwork of individual bilateral agreements between the United States and EU member states. For the first time, EU carriers could fly from any EU city to any US airport, and vice versa — eliminating country-of-origin restrictions that had previously limited, for example, British Airways to serving only routes originating in the UK.
Prior to the agreement, the US-EU transatlantic market served 55 million passengers on 385 flights per day in each direction across 235 nonstop city pairs operated by 45 airlines. Research by ESRI (Ireland) estimated that fare reductions of 20% on newly liberalized routes would increase US arrivals into the five EU countries that previously lacked bilateral Open Skies agreements (UK, Ireland, Greece, Spain, Hungary) by 7.3%, while redistributing traffic away from EU countries that already had such agreements.