The FAA issued a Special FAR on Friday that prohibits “certain flight operations” in a portion of the Simferopol Flight Information Region (FIR) by all U.S. airlines and commercial operators, and–with narrow exceptions–those with a U.S. airman certificate and operators of U.S.-registered civil aircraft. This prohibited area includes sovereign Ukrainian airspace over the Crimean Peninsula and the associated Ukrainian territorial sea, as well as international airspace managed by Ukraine over the Black Sea and the Sea of Azov. The SFAR will remain in effect for one year.

The FAA said the rule was prompted by the Russian Federation’s issuance of a notam on March 28 “purporting to establish unilaterally a new FIR, effective April 3, 2014, in a significant portion of the Simferopol (UKFV) FIR,” following Russia’s annexation of Crimea.

“In the FAA’s view, the potential for civil aircraft to receive confusing and conflicting air traffic control instructions from both Ukrainian and Russian ATS providers while operating in the portion of the Simferopol FIR covered by this SFAR is unsafe and presents a potential hazard to civil flight operations in the disputed airspace,” the FAA said.