The Federal Aviation Administration issued a warning in April barring American air carriers from flying over the Crimea region in Ukraine, citing safety concerns. The restricted region is about 200 miles northeast of the area of Thursday’s Malaysia Airlines crash site, which wasn't included in FAA warnings. 

The rule was posted to the agency’s web site on April 25 and is to remain in effect for one year.

The United Nation’s International Civil Aviation Organization and aviation authorities in most countries also issued similar notices.

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 (UKFV) FIR covered by this SFAR is unsafe and presents a potential hazard to civil flight operations in the disputed airspace,” the agency wrote.

“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.”