Story highlights With Russia operating in Syria, U.S. pilots have orders to change flight paths if there is a Russian plane within 20 nautical miles

The diversion was the first since Russia began military operations in Syria at the end of last month

Washington (CNN) The U.S. military diverted two aircraft over Syria to ensure they could maintain a safe flying distance from a Russian fighter aircraft in the same area, according to Captain Jeff Davis, Pentagon spokesman.

It was the first time the U.S. needed to do so since Russia began military operations in Syria at the end of last month.

The two planes were F-16s that had departed from Turkey's Incirlik air base and were on their way to a location near the ISIS stronghold of Raqqa, a senior defense official told CNN. The U.S. aircraft that diverted were not able to complete their mission, the official said.

Since the Russians began operating in Syrian airspace, U.S. pilots have been under orders to change their flight path if there is a Russian plane within 20 nautical miles, according to the official.

Davis said the incident happened in the last few days but offered few additional details.

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