Washington, July 17 (Reuters): Aviation safety authorities in the US and Europe warned pilots in April about potential risks flying in or near Ukraine airspace, where a Malaysian passenger airliner went down today.

The US Federal Aviation Administration on April 23 issued a “special notice” regarding Ukrainian airspace to US aviators and air carriers advising them not to fly in airspace around the Crimean city of Simferopol without special approval of the US government. The notice also warned US operators and pilots flying in other parts of Ukraine, including Kiev, Lvov, Dnepropetrovsk and Odessa, to “exercise extreme caution due to the continuing potential for instability.” The warning remains in effect until April 23, 2015.

International aviation agencies in April also had warned pilots and airlines to avoid the airspace around Simferopol. Agencies including the European Aviation Safety Agency and ICAO, a UN civil aviation agency, warned that airlines faced “serious risks” in the area and advised airlines to take alternate routes.

British Airways said today that it was keeping its once-a-day route between Heathrow airport and Kiev under review. “Our flights are not using Ukrainian airspace, with the exception of our once-a-day service between Heathrow and Kiev,” a British Airways spokeswoman said.

Germany's largest airline Deutsche Lufthansa AG, Russia’s state-controlled Aeroflot and Turkish Airlines would steer clear of east Ukrainian air space after the crash.