ARCHIVED - The Treaty on Open Skies

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Backgrounder / March 6, 2007 / Project number: BG-07.006

The Treaty on Open Skies entered into force on January 1, 2002.  The Treaty establishes a regime of unarmed aerial observation flights over the entire territory of its participants and is designed to enhance mutual understanding and confidence by providing all participants with the opportunity and means of gathering information about military forces and activities of concern to them. This Treaty seeks to enhance openness and transparency between States Parties through the observation and verification of areas such as military installations and facilities, industrial complexes, airports, seaports.  It responds to the desire of many countries to find a means of building confidence, stability and predictability in the arms control and verification process.

States Parties have quotas of annual observation flights to be conducted and received.  Observation flights are unrestricted and occur no sooner than 24 hours after the Observing State presents its flight plan to the Receiving State.  They are normally conducted in the Observing State's aircraft, with the national escorts of the Receiving State onboard.  Observers from other States Parties may also be present.


The concept of Open Skies was first proposed by American President Eisenhower to Soviet Premier Khrushchev at the Geneva Conference of 1955.  The Soviets promptly rejected the concept and it lay dormant for several years.  In May 1989, the United States reintroduced the idea of Open Skies as an instrument of security and confidence-building in the arms control and verification process.  25 nations signed the Treaty on Open Skies in Helsinki, Finland, on March 24, 1992.  Canada, a leading proponent, was designated co-depositor of the Treaty with Hungary. 

The Treaty on Open Skies is of unlimited duration and is the first treaty of its kind to extend well beyond European boundaries, "from Vancouver to Vladivostok."

The first Open Skies trial flights were conducted by Canada and Hungary during the treaty negotiation process.  Canada overflew Hungary on January 6, 1990, and the Hungarians conducted a reciprocal overflight of Canada on January 16, 1992.  Russia also completed a trial overflight in Canada on August 6, 1997.  These trial flights demonstrated the viability of the Open Skies concept. 

The first formal observation flight over Canada in support of the Treaty on Open Skies was conducted by the Russian Federation and took place on September 10, 2004.  The Russian aircraft, a mission-configured Tupolev 154M, flew from Ottawa to Winnipeg at low altitude (between 8,000 and 9,000 feet) and overflew various cities, industrial complexes, military installations and infrastructure, as well as other designated objects of interest.  The aircraft refuelled in Winnipeg before returning to Ottawa the same day.

Signatory States

The Treaty on Open Skies was originally negotiated between members of NATO and the former Warsaw Pact as a means of building confidence in the arms control process.  Although the Warsaw Pact ceased to exist before the treaty was signed in Helsinki, the former members of that alliance nevertheless continued to support Open Skies.

The following 34 states have ratified the Treaty on Open Skies: Belarus, Belgium, Bosnia-Herzegovina, Bulgaria, Canada, the Republic of Croatia, the Czech Republic, Denmark, Estonia, Finland, France, the Republic of Georgia, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Russia, the Slovak Republic, Slovenia, Spain, Sweden, Turkey, Ukraine, the United Kingdom and the United States.

Canada and Hungary are the depositories of the treaty in recognition of their special contribution to the Open Skies process.  "Depository" countries maintain treaty documents and provide administrative support.

Open Skies Aircraft

All aircraft used for Open Skies are subjected to rigorous certification standard and inspection to ensure that their sensors are approved and conform to the standards of the Treaty.  Aircraft are unarmed but may be equipped with panoramic, framing and video cameras, infrared line scanning systems and synthetic aperture radar that can operate day and night in any weather.  These sensors must be commercially available to all signatories.  Imagery resolution is limited to 30 centimetres.

Canada uses the CC130 Hercules aircraft equipped with a "SAMSON" sensor pod to conduct flights over other treaty nations.  The pod is a converted CC130 fuel tank modified to carry the permitted sensors, along with associated on-board mission systems. A consortium of nations consisting of Belgium, Netherlands, Luxemburg, Canada, France, Greece, Italy, Norway, Portugal, and Spain own and operate this system.  The costs of maintaining the SAMSON Pod are shared, based on each nation's flight quota and actual use.

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