Open Skies Treaty

International agreement that allows signatory nations to conduct unarmed aerial observation flights over the territory of other participating members. Designed to enhance confidence and security, the Open Skies Treaty gives each party the right to gather information about the military forces and activities of other parties.

The original open-skies concept was proposed by U.S. president Dwight D. Eisenhower to Soviet Premier Nikita Khrushchev in 1955. At the time, the Soviets rejected the concept, and it lay dormant for a generation. In May 1989, the initiative was reintroduced by President George H. W. Bush and signed on March 24, 1992, in Helsinki, Finland. The U.S. Congress ratified the treaty in 1993. The treaty entered into force by January 1, 2002, when it received final ratification by the members of the North Atlantic Treaty Organization (NATO).

The main provision of the Open Skies Treaty allows each member state to observe military forces and actions in the territories of other members by permitting the installation of photographic and advanced sensory equipment on aircraft and satellites. Images collected by a member state are available to any other member willing to pay the costs of reproduction. The treaty also ensures that all surveillance equipment covered under the treaty will be available to all participants in the regime. Signatories agree on an annual quota of observation flights each member state is willing to receive and send out. The treaty covers the national territories—land, islands, and the internal and territorial waters—of all the member states. It is also of unlimited duration and open to other states based on certain stated qualifications.

Provisional application of portions of the treaty took place between 1992 and 2002, and formal observation flights have been in place since August 2002. Since the signature of the Open Skies Treaty in 1992, the security environment in Europe has changed significantly. Nevertheless, Open Skies is the most wide-ranging international effort to date to promote openness and transparency of military forces and activities. It thus remains an important element of the European security structure, along with the Treaty on Conventional Armed Forces in Europe (CFE) and the Vienna Document 1999 agreement on confidence- and security-building measures (CSBMs) under the auspices of the Organization for Security and Cooperation in Europe (OSCE).