The two sites were spotted by the warplanes as they were on a protection flight over the airfield in Kurdish-controlled territory where some 1,000 US troops parachuted and set up base on Thursday, the pilots explained.

"We were pretty much in the vicinity of the airfield, protecting any threats from the south that might impact the guys in the north," said one of the pilots who asked to be named as "Pancho".

"Tonight we were flying at very high altitude, at a significant stand-off from the threat, so we were at a location where their missiles couldn't reach us," said another pilot, whose nickname was "Wayd".

WAR.WIRE