Iraqi pilots who have joined the so-called ’Islamic State of Iraq and the Levant’ (ISIL) terrorist group in Syria are training members of the group to fly in three captured fighter jets.

Iraqi pilots who have joined the so-called 'Islamic State of Iraq and the Levant' (ISIL) terrorist group operating in Syria are training members of the group to fly in three captured fighter jets, the opposition UK-based Syrian Observatory said on Friday.

"It was the first time the militant group had taken to the air," it added.

ISIL has been flying the planes over the captured al-Jarrah Syrian military airport east of Aleppo, said Rami Abdulrahman, who runs the Observatory, citing witnesses in Syria's northern Aleppo province.

"They have trainers, Iraqi officers who were pilots before for (former Iraqi president) Saddam Hussein," he said.

"People saw the flights, they went up many times from the airport and they are flying in the skies outside the airport and coming back."

It was not clear whether the jets were equipped with weaponry or whether the pilots could fly longer distances in the planes, which witnesses said appeared to be MiG 21 or MiG 23 models captured from the Syrian national military.

The countryside east of Aleppo city is one of the main bases occupied by ISIL in Syria. The terrorist group also seized areas in Syria and neighboring Iraq.