During the hostilities between Ukraine and Russia, the threat of military action against a civilian airliner has been in the air for months.
The Federal Aviation Administration prohibited U.S. airlines in April from flying over Crimea, but because of concerns about air-traffic control rather than military action.
The FAA took the action April 25, which is to remain in effect for one year, because of a dispute between Ukraine and Russia about which country controlled the airspace in the Simferopol region, which covers the Crimean peninsula.
The Russian Federation declared March 28 that it controlled the airspace over Crimea, as well as international airspace above the Black Sea and Sea of Azov. In response, Ukraine created a prohibited area over the Crimean peninsula for flights below 29,000 feet.
Because of the dispute, the International Civil Aviation Organization, a branch of the United Nations, warned airlines April 3 to avoid the area.
"In addition, political and military tension between Ukraine and the Russian Federation remains high, and compliance with air traffic control instructions issued by the authorities of one country could result in a civil aircraft being misidentified as a threat and intercepted or otherwise engaged by air defense forces of the other country," FAA said.