evidence: On April 23, the FAA issued a Notice to Airman (NOTAM) prohibiting U.S. carriers from flying over the Crimean region and portions adjacent to the Black Sea and the Sea of Azov. It didn't cover the air space where MH17 crashed. "This action was taken due to the unilateral and illegal action by Russia to assert control over Crimean air space, including international air space administered by Ukraine, without agreement by the International Civil Aviation Organization (ICAO)," the FAA said in a statement. Similar notices were issued by other countries.