The U.S. Air Force has flown the first observation flight under the much-debated Open Skies Treaty in 2018 over Ukraine. The mission comes as Russian and Ukranian forces hold dueling missile drills amid inflamed tensions following a violent skirmish in the Kerch Strait between the Black Sea and the Sea of Azov. The U.S. military announced it had conducted the “extraordinary flight” over unspecified areas of Ukraine on Dec. 6, 2018. Earlier plane spotters using online flight tracking software had recorded one of the Air Force’s two aging OC-135B Open Skies observation aircraft departing from Kiev. Russia's Tu-214ON Open Skies aircraft later took off from Moscow, but it is unclear if it was on its own mission under the terms of the treaty.

“The timing of this flight is intended to reaffirm U.S. commitment to Ukraine and other partner nations,” the Pentagon said in a brief statement on Dec. 6, 2018. “Russia's unprovoked attack on Ukrainian naval vessels in the Black Sea near the Kerch Strait is a dangerous escalation in a pattern of increasingly provocative and threatening activity.” The Open Skies treaty, which entered force in 2002, gives signatories the right to conduct observation flights and collect imagery over the territory of other member states. The agreement sets out how high fidelity that imagery can be and at what altitude the aircraft can gather it. The deal ostensibly is to allow countries to monitor foreign military movements to ensure that they are non-hostile and reduce the chances for dangerous escalations and potential conflicts.