Open Skies Agreements: How International Aviation Treaties Shape Where You Can Fly

When you book a flight from London to Tokyo, it seems like a simple transaction: you pay the fare, the airline flies the route. But behind that booking lies an intricate web of international treaties, bilateral agreements, and geopolitical negotiations that determine which airlines can fly between which countries, how many flights they can offer, and even what prices they can charge. These agreements — collectively known as air service agreements (ASAs) — form the legal backbone of international aviation, and the most liberal form of ASA, the Open Skies agreement, has transformed the industry over the past three decades.

The Chicago Convention and the Birth of Air Law

Modern international aviation law traces its origins to the Convention on International Civil Aviation, signed in Chicago in December 1944. The Chicago Convention established the International Civil Aviation Organization (ICAO) and codified the principle that every country has complete and exclusive sovereignty over the airspace above its territory. This means that no airline can fly into or over a foreign country without that country's permission — a principle that applies equally to the smallest island nation and the largest superpower.

The Chicago Convention delegates attempted to create a multilateral framework for international air services but failed. The United States, which emerged from World War II with the world's largest aviation industry, favored an open market. The United Kingdom, whose airlines were smaller and less competitive, demanded protective regulation. The impasse meant that international air service rights would be negotiated bilaterally, between individual pairs of countries, for the next half-century.

The Nine Freedoms of the Air

Air service agreements are structured around a framework known as the freedoms of the air — a set of traffic rights that range from the most basic (overflying a country's territory) to the most commercially valuable (operating domestic flights within a foreign country). The most commonly referenced freedoms are:

1. First Freedom: The right to fly over a foreign country without landing.
2. Second Freedom: The right to land in a foreign country for technical reasons (refueling) without picking up or discharging passengers.
3. Third Freedom: The right to carry passengers from your home country to a foreign country.
4. Fourth Freedom: The right to carry passengers from a foreign country back to your home country.
5. Fifth Freedom: The right to carry passengers between two foreign countries on a flight that originates or terminates in your home country.
6. Sixth Freedom: The right to carry passengers between two foreign countries via your home country (essentially combining Third and Fourth Freedom rights).
7. Seventh Freedom: The right to carry passengers between two foreign countries without the flight touching your home country at all.
8. Eighth Freedom (Consecutive Cabotage): The right to carry passengers between two points within a foreign country as part of a flight originating in your home country.
9. Ninth Freedom (Stand-Alone Cabotage): The right to operate purely domestic flights within a foreign country.

In practice, most bilateral ASAs grant Third and Fourth Freedom rights as a matter of course. Fifth Freedom rights are more restricted and are often the subject of intense negotiation. Seventh, Eighth, and Ninth Freedom rights are rarely granted — cabotage, in particular, is one of the most jealously guarded prerogatives of national aviation sovereignty.

The Bermuda Model and Its Limitations

For most of the postwar period, bilateral ASAs followed what is known as the Bermuda model, named after the landmark 1946 agreement between the United States and United Kingdom. Bermuda-type agreements specified which airlines could serve which routes, often restricting service to one or two designated carriers per country. They frequently included capacity controls (limiting the number of seats each airline could offer) and sometimes even fare coordination through IATA's tariff conferences.

The Bermuda model protected national carriers — flag airlines like British Airways, Air France, and Japan Airlines — from foreign competition. But it also restricted consumer choice and kept fares artificially high. A passenger flying from London Heathrow (LHR) to New York JFK in the 1980s could choose only between British Airways and the designated American carrier (initially Pan Am, later United or American). Fares were coordinated through IATA, meaning that the competing airlines often charged identical prices.

The U.S. Open Skies Revolution

The United States, which had deregulated its domestic aviation market in 1978, began pursuing a similar liberalization of international services in the early 1990s. The policy, formally known as Open Skies, aimed to replace the restrictive Bermuda-type ASAs with agreements that removed limits on which airlines could serve which routes, how many flights they could operate, and what fares they could charge.

The first U.S. Open Skies agreement was signed with the Netherlands in 1992. The Netherlands was chosen strategically: Amsterdam Schiphol (AMS) was KLM's hub, and the agreement gave U.S. carriers unrestricted access to one of Europe's most important connecting airports. The deal was wildly successful — passenger traffic between the two countries surged, fares dropped, and new routes were launched that had been impossible under the previous restrictive ASA.

The Netherlands agreement became the template. Over the next two decades, the United States signed Open Skies agreements with more than 130 countries, creating a global network of liberal aviation markets. European countries initially resisted, but as more of their neighbors signed Open Skies deals with the U.S., holdouts found themselves at a competitive disadvantage. The United Kingdom — historically the most protective of Heathrow access — finally signed an Open Skies-style agreement in 2008 as part of the broader EU-U.S. Air Transport Agreement.

The EU Single Aviation Market

Within Europe, an even more radical liberalization occurred. The creation of the EU Single Aviation Market in the 1990s granted all EU-registered airlines the right to operate any route within the European Union, including domestic routes in other member states (Ninth Freedom cabotage). This was unprecedented: for the first time in aviation history, airlines from one country could freely compete on domestic routes within another sovereign nation.

The EU Single Market created the conditions for the explosive growth of low-cost carriers like Ryanair (an Irish airline that became the largest carrier on many domestic routes in the UK, Italy, and Spain) and easyJet (a British airline that serves dozens of intra-European routes from bases across the continent). Without the Single Market, these carriers could never have achieved the scale and route networks that made their low-cost models viable.

The Gulf Carrier Controversy

Open Skies agreements have also created geopolitical flashpoints. The most contentious example involves the so-called Gulf carriers — Emirates, Qatar Airways, and Etihad Airways — whose rapid expansion has been facilitated by Open Skies agreements with the United States and European countries. U.S. and European legacy carriers have accused the Gulf airlines of receiving massive government subsidies (including free airport infrastructure, below-market fuel, and direct cash injections) that distort competition.

The Gulf carriers deny receiving unfair subsidies, arguing that their governments are simply investing in aviation as a core economic development strategy — no different from the billions in subsidies that U.S. airlines have received through bankruptcy protections, tax breaks, and COVID-era bailouts. The dispute has generated thousands of pages of lobbying documents, academic studies, and media coverage, but no resolution. The Open Skies agreements remain in place, and the Gulf carriers continue to expand.

Impact on Passengers

For passengers, Open Skies agreements have delivered clear benefits. Research by the International Transport Forum found that routes covered by Open Skies agreements have, on average, 25 percent more frequencies and 15 to 20 percent lower fares than comparable routes governed by restrictive bilateral agreements. The increased competition drives innovation in service, and the expanded route networks make it possible to fly between city pairs that were previously unserved or required circuitous connections.

The consumer benefits are most visible on routes where Open Skies replaced particularly restrictive regimes. The 2008 EU-U.S. agreement, which opened Heathrow to any qualified EU and U.S. carrier, led to a surge of new services from airlines that had been locked out of LHR for decades. Within two years of the agreement, passengers on transatlantic routes from Heathrow had access to more airlines, more frequencies, and lower average fares than at any previous time.

Limitations and Critics

Open Skies is not without critics. Developing countries argue that liberalization disproportionately benefits airlines from wealthy nations, which have the capital to launch new routes, while local carriers are overwhelmed by foreign competition. Several African nations have been reluctant to implement the Single African Air Transport Market (SAATM), fearing that their nascent airlines would be crushed by better-funded competitors from Ethiopia, South Africa, or Kenya.

Labor unions have also raised concerns, arguing that liberalization puts downward pressure on wages and working conditions as airlines compete to minimize costs. The growth of flag-of-convenience carriers — airlines based in countries with minimal regulatory oversight — has been cited as a risk of overly permissive Open Skies regimes.

The Future of Aviation Treaties

The trend toward further liberalization continues, though unevenly. The International Civil Aviation Organization has endorsed the concept of multilateral liberalization, and regional blocs in Latin America, Southeast Asia, and Africa are negotiating their own versions of open aviation markets. However, full global liberalization — a single worldwide aviation market with no restrictions on which airlines fly where — remains a distant prospect, blocked by the same sovereignty concerns and protectionist instincts that prevented it at Chicago in 1944.

For passengers, the practical implication is simple: the more liberal the aviation agreement between two countries, the more airlines will serve the route, the more flights will be available, and the lower fares will tend to be. The invisible hand of international aviation law may never make headlines, but it shapes every itinerary you book.