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.  READ: John Kerry raises Syria no-fly zone despite Obama's skepticism  "We are taking action to ensure" the planes don't come too close to each other, he said, indicating there had only been one incident so far. There is no sign the two aircraft communicated with each other.  In the recent incident, the Russian plane came within the 20 nautical mile interval. The new U.S. rules were instituted specifically because there is no agreement with the Russians yet on maintaining mutual flight safety rules and practices. In fact, the incident happened in the days after the first round of technical talks with Russia on that issue.  Without that agreement, the official said, U.S. pilots cannot count on the Russians to fly under standard safety procedures.  The official emphasized the reason for the new rules is concern about keeping American pilots safe, given the long history of aggressive Russian military intercepts against U.S. aircraft.
The U.S. military has had to divert 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.