The Treaty on Open Skies

Fact Sheet
Bureau of Arms Control, Verification, and Compliance
March 8, 2016

The Treaty on Open Skies is an agreement that allows for unarmed aerial observation flights over the entire territory of its participants. Its purpose is to promote stability through openness and transparency of military forces and activities. Open Skies enhances mutual understanding and confidence by giving all participants, regardless of size, a direct role in gathering information about areas of concern to them.

Origin and Purpose

The original concept of mutual aerial observation was proposed by President Eisenhower in 1955 and the Treaty concept was re-introduced as a multilateral initiative by President George H.W. Bush in 1989. The Treaty on Open Skies was negotiated by the then-members of NATO and the Warsaw Pact, and was signed in Helsinki, Finland, on March 24, 1992. The Treaty entered into force on January 1, 2002, and currently has 34 States Parties. Since 2002, through 2015, States Parties have successfully conducted more than 1200 observation flights over each other’s territory. In addition, U.S. Open Skies flight teams have supported a variety of humanitarian and environmental missions around the world and responded to short-notice requests for imagery following natural disasters in the United States.

Despite significant changes to the security environment in Europe since signature of the Open Skies Treaty in 1992, the Treaty continues to contribute to European security by enhancing openness and transparency among the Parties.


The 34 States Parties to the Open Skies Treaty are: Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Romania, Russian Federation, Slovak Republic, Slovenia, Spain, Sweden, Turkey, United Kingdom, Ukraine, and United States. Kyrgyzstan has signed but not ratified the Treaty.

The Treaty is of unlimited duration and is open to accession by other States. States of the former Soviet Union which have not already become States Parties to the Treaty may accede to it at any time. Applications from other interested States are subject to a consensus decision by the Open Skies Consultative Commission (OSCC), the Vienna-based organization charged with facilitating implementation of the Treaty, to which all States Parties belong. Eight states have acceded to the Treaty since entry into force: Finland, Sweden, Latvia, Bosnia and Herzegovina, Croatia, Slovenia, Estonia, and Lithuania.

Basic Elements of the Treaty

Territory: The Open Skies regime covers the territory over which the State Party exercises sovereignty, including land, islands, and internal and territorial waters. The Treaty specifies that the entire territory of a State Party is open to observation. Observation flights may be restricted only for reasons of flight safety, not for reasons of national security. As such, all areas of the United States may be overflown, including military installations, industrial sites, and Washington, D.C.

Aircraft: Observation aircraft are normally provided by the observing Party, but the observed Party has the right to provide the observation aircraft instead. However, in order to do so the aircraft must contain at least one of all four types of sensors. To date, no State Party has certified an aircraft with all four types of sensors aboard.

All Open Skies aircraft and sensors must pass certification and preflight inspection procedures to ensure that they are compliant with Treaty standards. Certified Open Skies aircraft include:

Bulgaria An-30
Hungary An-26
POD Group C-130 (Canada, France, Italy)
Romania An-30
Russian Federation An-30 and Tu-154
Sweden Saab-340
Turkey Casa CN-235
Ukraine An-30
United States OC-135B

Sensors: Open Skies aircraft may have video, optical panoramic and framing cameras for daylight photography, infrared sensors for a day/night capability, and synthetic aperture radar for a day/night, all weather capability. Technical implementing agreements are required prior to the deployment of infrared and synthetic aperture radar sensors. Photographic image quality permits recognition of major military equipment (e.g., permits a State Party to distinguish between a tank and a truck), thus allowing significant transparency of military forces and activities. Technology advancements have made film cameras increasingly obsolete and, consequently, many States Parties, including the United States, are actively preparing for the transition to digital electro-optical sensors. The Russian An-30 was certified with a digital electro-optical sensor in April 2014. All equipment used in Open Skies implementation must be commercially available to all States Parties.

Quotas: Each State Party is obligated to receive a certain number of observation flights, i.e., its passive quota. Each State Party may conduct as many observation flights – i.e., its active quota - as its passive quota. The Russian Federation and the United States each have an annual passive quota of 42, while the other States Parties have quotas of 12 or fewer. The Parties negotiate the annual distribution of the active quotas each October for the following calendar year. Approximately 100 observation flights are conducted each year. In recent years, the United States has received 4-9 observation flights from Russia and we have conducted 14-16 flights over Russia each year.

Data Sharing/Availability: Imagery collected from Open Skies missions is available to any State Party upon request, with the cost being covered by the requesting party. As a result, each State Party may obtain all data collected under the Treaty, not just the data from flights it conducts. Thus, the United States has access to data collected from all 25-35 flights conducted over Russia annually.

Implementation of the Treaty

The United States considers the Open Skies Treaty to be a key element of our Euro-Atlantic security architecture. The broad cooperation by all Treaty Parties, especially in sharing observation flights, is but one hallmark of the Treaty’s success. Future implementation depends on the sustainability of the aircraft fleet and transition to digital sensors. Enhanced cooperation among States Parties in this area is under consideration in the OSCC.

The OSCC continues to address modalities for conducting observation missions and other implementation issues. The OSCC has monthly plenary meetings during three several-month sessions each year. The OSCC has several informal working groups that take up technical issues related to sensors, notification formats, aircraft certification and rules and procedures. The OSCC’s main functions are to:

-- consider questions related to compliance with the Treaty;
-- seek to resolve ambiguities and differences of interpretation that emerge during Treaty implementation;
-- consider and decide on applications for accession to the Treaty;
-- review the distribution of active quotas annually.

The OSCC was established by Article X and Annex L of the Treaty, and has been in session since Treaty signature in March 1992. The OSCC takes decisions by consensus, and has adopted 190 Decisions since its inception. OSCC Decisions enter into force with the Treaty and have the same duration as the Treaty.