In May 1989, the U.S. reintroduced the idea of Open Skies as an instrument of confidence-building. The Open Skies Treaty was developed in the framework of Confrence for Security and Co-operation in Europe (CSCE; now the Organization for Security and Co-operation in Europe, OSCE). The Open Skies Treaty was finally signed on March 24, 1992. The Treaty has been ratifed by 26 parties. The treaty is unusual in naming two depositories, both the Government of Canada and the Government of Hungary, with instruments of ratification or accession being able to be submitted to either one or both.
The Treaty enhances mutual understanding and international confidence by giving all participating countries, regardless of size, a direct role in gathering information about military forces and activities of concern to them. It permits military aerial observation flights to be flown at short-notice over the territory of one signatory by representatives of another, subject only to the constraint of routine air traffic control procedures.
See also: Treaties