The U.S. military says it is unaware of any flight operations by Islamic State (IS) militants "in Syria or elsewhere."
U.S. Central Command made the comment after a monitoring group reported that IS militants were being trained to fly in three captured fighter jets.
Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, said on October 17 that witnesses have reported seeing warplanes take off from an air base east of the Syrian city of Aleppo, in an area that is under the control of IS militants.
U.S. Central Command spokesman Colonel Patrick Ryder, using another acronym for the militant group, said: "We're not aware of ISIL conducting any flight operations in Syria or elsewhere."
Further to the northeast, U.S. warplanes again launched strikes on the Syrian town of Kobani, where Kurdish forces have been under siege from the militant group for weeks.