Treaty on Open Skies

The Treaty on Open Skies authorizes the militaries of States Parties to conduct unarmed reconnaissance flights over other States Parties' territories.

  • Ratified
  • Signed, not ratified
  • Withdrawn

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Ratified (33)

Signed, not ratified (1)

Withdrawn (2)

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24 March 1992

1 January 2002

Entered into Force



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Treaty Overview

About the Treaty

  • Depositaries: Canada and Hungary

Entered into Force

1 January 2002 – Entry into force occurred 60 days after the deposit of the 20th instrument of ratification on 2 November 2001. The requisite instruments of ratification include those of the Depositaries, and those States Parties that are obligated to accept eight or more passive observation flights (Russia and Belarus–42, United States–42, Canada–12, France–12, Germany–12, Italy–12, Turkey–12, Ukraine–12, and the United Kingdom–12).


The idea of a regime of unarmed aerial observation flights to promote confidence, predictability, and stability was first suggested by US President Dwight Eisenhower in 1955. On 12 May, 1989, U.S. President George Bush proposed the creation of an Open Skies regime, which expanded on President Eisenhower’s concept. Under this regime, the participants would voluntarily open their airspace on a reciprocal basis, permitting the overflight of their territory in order to strengthen confidence and transparency with respect to their military activities. In December 1989, the participants of the North Atlantic Council Meeting in Brussels issued the “Open Skies: Basic Elements” document calling for the establishment of an Open Skies regime for members of NATO and the Warsaw Pact to promote openness and transparency, build confidence, and facilitate verification of arms control and disarmament agreements.

During the meeting between NATO and the Warsaw Pact in Ottawa on 12 February, 1990, Canada and Hungary launched a similar initiative. Further negotiations in Vienna supported by the Organization for Security and Cooperation in Europe (OSCE) Conference Services with the participation of the Member States of NATO and the Warsaw Pact were concluded on 24 March 1992 with the signature of the Treaty on Open Skies.


The Treaty establishes the Open Skies regime for the conduct of short-notice, unarmed, observation flights by States Parties over the territories of other States Parties. The Treaty gives each State Party the right to conduct and the obligation to accept observation flights over their territory. The Treaty establishes a “passive quota” for each State Party, which is the total number of observation flights that each State Party is obliged to accept over its territory, and an “active quota,” which is the number of observation flights that a State Party shall have the right to conduct over the territory of each of the other States Parties. A State Party’s “active quota” cannot exceed its “passive quota,” and a single State Party cannot request more than half of another State Party’s “passive quota.” Annex A details the specific numbers for both quotas. The Treaty entitled the States Parties to form groups and redistribute their “active quotas,” and to have common total “active and passive quotas.”

The Treaty obligates the States Parties to conduct observation flights using designated observation aircraft, which could belong to an observing State Party or be provided by the State Party under observation. To conduct an observation flight, an observing State Party must provide at least 72-hour notice to the State Party it wishes to observe. Receipt of the notification must be acknowledged within 24 hours. The observing State Party must provide a mission plan to the observed State Party at least 24 hours before the commencement of an observation flight. The mission plan may detail an observation flight that allows for the observation of any point on the entire territory of the observed Party. The observed State Party may propose changes to the submitted mission plan. Under certain conditions, deviations from the mission plan could be permitted. The observation mission must be completed within 96 hours of the observing State Party’s arrival unless otherwise agreed.

The Treaty specifies four types of sensors with which observation aircrafts could be equipped, including optical panoramic and framing cameras, video cameras with real-time display, infra-red line-scanning devices, and sideways-looking synthetic aperture radar. A copy of all data collected by the observing State Party shall be supplied to the host country, while other States Parties shall receive a mission report and have the option of purchasing the data collected by the observing State Party.

Verification and Compliance

The Treaty established an Open Skies Consultative Commission (OSCC) that conducts its work by consensus. The OSCC is in charge of the questions related to compliance with the Treaty, and seeks to resolve ambiguities and differences of interpretation should they occur, consider applications for accession to the Treaty, and take care of technical and administrative measures. The OSCC convenes in monthly plenary meetings at the headquarters of the Organization for Security and Cooperation in Europe (OSCE) in Vienna.

Review Conference

The Treaty provides for a periodic review conference to review the Treaty’s implementation to be convened three years after the entry into force of the Treaty and at five-year intervals thereafter.

Point of Contact

OSCE Secretariat
Wallnerstrasse 6
1010 Vienna
Phone: +43 1 514 36 6000
Fax: +43 1 514 36 6996




On 15 January, the Russian Foreign Ministry announced that Russia would initiate steps to withdraw from t

he Open Skies Treaty. Russian Foreign Minister Sergei Lavrov later suggested that Russia would reconsider should the United States return to the treaty. In response to a question regarding Lavrov’s statement at press briefing on 2 February US State Department Spokesperson Ned Price indicated that the Biden Administration was “studying the issue” and would “take a decision in due course.”

On 19 May, the Russian State Duma adopted a bill to formally endorse a withdrawal from the Open Skies Treaty. The bill cited the United States’ continued ability to receive information acquired via the treaty from its NATO allies as precipitating the decision.

On 27 May, U.S. Deputy Secretary of State Wendy Sherman informed the Russian government that the United States will not rejoin the Open Skies Treaty.


On 23 January 2020 Voice of America reported that the National Defense Authorization Act of 2020 included funding for new American spy planes, seemingly contradicting U.S. administration messaging about remaining party to the Treaty.

On 22 May 2020, U.S. Secretary of State Michael Pompeo announced the United States’ intention to withdraw from the Treaty on the Open Skies. Pompeo cited claimed Russian violations of the Treaty as precipitating U.S. withdrawal. On 22 November 2020, the United States formally withdrew from the treaty.



On 21 February, the U.S. conducted the first routine Open Skies surveillance mission over Russia since 2017. The U.S.’s 6 December 2018 flight over Ukraine was technically “extraordinary,” or outside of routine treaty flights.

From 26-30 March, Russia conducted routine surveillance flights over the western U.S.

On October 7, Chairman of the U.S. House Foreign Affairs Committee Rep. Engel sent a letter to National Security Advisor Robert O’Brien voicing concern over the Trump administration apparently considering withdrawal from the Open Skies Treaty. A State Department spokesperson suggested the reason for withdrawing was doubt over Russia’s compliance with the treaty.


On 16 May, the U.S. House Armed Services Committee scuttled the U.S. Air Force’s proposal to replace two aging OC-135 aircraft with new aircraft. The replacement aircraft would have been the first new aircraft in the U.S.’s Open Skies fleet since 1967.

On 13 August, the John S. McCain National Defense Authorization Act was signed into law by President Trump. The Act suspended funding for the Treaty until Russia is in “complete compliance with [its] obligations,” although a U.S. State Department official clarified that the U.S. was not pulling out of the treaty.

On 12 September, the Russian Federation announced that the U.S. had denied access for two Russian Tu-214ON surveillance planes to take part in an Open Skies inspection. The Russian government alleged that no explanation was given for the refusal, and no U.S. explanation was immediately forthcoming. The Tu-214ON planes feature advanced surveillance technology that U.S. politicians have previously cited as worrisome.

On 6 December, the U.S. conducted an Open Skies flight over Ukraine at the country’s request. The flight was technically “extraordinary,” or outside of Ukraine’s yearly allotted number of requests, and the United States stated explicitly that the flight’s purpose was to demonstrate to Russia its commitment to Ukraine’s defense. According to observers, the flight did not likely fly close to contested areas.



Mid-to late 2017 saw a series of tit-for-tat diplomatic maneuvers by the U.S. and Russian Federation regarding the Open Skies treaty. In June, the U.S. alleged that Russia was in violation of the treaty for limiting permitted flight lengths over Kaliningrad by the U.S. The U.S., in turn, announced plans to limit Russian flights over military facilities in Alaska and Hawaii. Late in 2017, the U.S. also announced that Russian crews were not welcome for overnight stays at its bases in the states of Georgia and South Dakota. In response, Russia announced that U.S. planes would be barred from launching flights from three military bases within its borders, from which previous Open Skies flights had been conducted. The country of Georgia also announced its resistance to allowing further Russian flights.

On 10-15 April, the Russian Federation carried out observation flights over the United States under the Treaty on Open Skies. Sergey Ryzhov, head of Russia’s National Nuclear Risk Reduction Center, confirmed that this was the ninth observation flight carried out by Russia in 2017.

On 6 December, the U.S. conducted an Open Skies flight over Ukraine at the country’s request. The flight was technically “extraordinary,” or outside of Ukraine’s yearly allotted number of requests, and the United States stated explicitly that the flight’s purpose was to demonstrate to Russia its commitment to Ukraine’s defense.


On 3 February Turkish military officials denied a Russian observation flight along the Syrian border and airfields that house NATO warplanes.

On 22 February, The Russian Federation requested permission to fly over American territory in a plane outfitted with high tech surveillance cameras. This request was met with skepticism and caution by many US government officials.

On 11 April, the U.S. State Department released its 2016 Report on Adherence to and Compliance with Arms Control, Nonproliferation, and Disarmament Agreements and Commitments. The report reiterated the previous year’s conclusions on Russian compliance with the Open Skies Treaty, citing imposed maximum flight distances and restricted access to Russian territory.

On 15 May, U.S. House Foreign Affairs Committee Chairman Ed Royce, Intelligence Committee Chairman Devin Nunes, and Armed Services Committee Mac Thornberry urged President Obama to deny Russia’s request to install digital equipment on Open Skies flights, accusing the Russian Federation of using the treaty to expand its espionage capabilities.

On 27 June, Russia became the first treaty member to install digital electric-optical sensors on its surveillance aircraft. Sergey Ryzhov, head of the National Nuclear Threat Reduction Center, stated that the new equipment is in full compliance with the requirements and limitations of the treaty.

On 28 June, the United States approved the Russian Federation’s request to fly over U.S. territory despite criticism over Russia’s use of advanced digital technology.



On 30 March, The United States of America and Ukraine planned an observation flight over Russia and Belarus under the Treaty on Open Skies.

On 5 June, the U.S. State Department released the 2015 Report on Adherence to and Compliance with Arms Control, Nonproliferation, and Disarmament Agreements and Commitments. The report concluded that the Russian Federation is in non-compliance with its treaty obligations to allow observation of its entire territory.

On 8 June many participants voiced their belief in the continued importance of the Treaty at the 3rd Open Skies Treaty Review Conference in Vienna, citing confidence building and promotion of openness of military forces.


On 21 January, the U.S. Defense Science Board issued a report advising the U.S. military to delay upgrading its Open Skies OC-135 reconnaissance planes. The report cited the easy accessibility of satellite imagery as a replacement for the planes’ reconnaissance trips.

On 17 April, U.S. officials confirmed that Russia canceled a scheduled U.S. surveillance flight over Russian territory in order to limit spying on Russian military activity on both sides of the Ukrainian border.

Mid-year, Russia received two Tu-214ON aircraft outfitted with special onboard surveillance systems, called the Open Skies Aviation Monitoring System (ASN ON). The Russian Ministry of Defense is the only nation to possess aircraft with the new technology.



On 28 August, the 1000th observation flight under the Open Skies Treaty took place. The aerial observations are used to build confidence.

On 2 September, it was announced that Russia began their “Open Skies” flight over the US. These will be the 28th and 29th observation flights conducted by the Russian military inspectors.

97 flights took place in 2013.


On 27 March, the CFE celebrated the 20th anniversary of the signing of the Treaty on Open Skies, and the 10th anniversary of its entry into force. The commemorative event held in Vienna was attended by all States Parties to the Treaty, the observers to the Treaty, and OSCE Partners.

100 flights took place in 2012.



States Parties to the treaty conducted ninety-five flights under the Treaty throughout the year.


The OSCC conducted the Second Treaty Review Conference on 7 to 9 June in Vienna. Chaired by the United States, Secretary of State Hillary Clinton addressed the conference and stressed U.S. commitment to the Treaty’s continued success.

In the Final Document of the conference, the State Parties agreed on the following:

  • to further cooperate on transparency measures
  • to press for expansion of members to the treaty
  • recognizing the challenges of maintaining aging Open Skies aircraft, as well as other financial burdens, such as the transition from film-based cameras to digital cameras
  • a reaffirmation of intention to address sensor categories and an establishment of minimum technical standards for Open Skies airfields in “the near future”
  • the willingness to assist other interested regions in the world as a model for aerial monitoring in order “to promote security and stability”

The States Parties also noted a total of over 670 flights have occurred since the Treaty’s entry into force in January 2002. They also emphasized their commitment to the treaty and the future Third Conference set for 2015.



One hundred flights were conducted under the treaty throughout the year.


A Benelux flight over Bosnia and Herzegovina on 20 August with observers from Canada, Norway, and the Czech Republic on board, marked the 500th flight conducted under the treaty.


The OSCC held the First Treaty Review Conference from 14 to 16 February in Vienna, and reaffirmed the importance and effectiveness of the regime as a transparency and confidence-building measure.

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