The planes, which are believed to be MiG-21 and MiG-23 jets, are capable of flying although it is unclear if they are equipped with missiles, according to the Syrian Observatory for Human Rights. The jets were seized from Syrian military airports now under IS control in the northern provinces of Aleppo and Raqa, according to the Britain-based group, which has a wide network of sources inside the war-torn country.
It said that former Iraqi army officers who once served under Saddam were supervising the training at the military airport of Jarrah, east of the city of Aleppo.
Witnesses have reported seeing planes flying at a low altitude to avoid detection by radar after taking off from Jarrah. It comes as the United States and its allies carry out a wave of air strikes on IS positions in Syria and Iraq.
The jihadists also control two other airports in Syria - Albu Kamal near the Iraqi border and Tabqa in Raqa province. IS has captured large parts of Syria and Iraq, committing atrocities and declaring an Islamic "caliphate".
After the US-led invasion of Iraq in 2003, some Sunni former officers from Saddam's army joined the ranks of the Islamic State of Iraq, a branch of al-Qaeda which later became IS.
Sniper and mortar fire from jihadists are preventing authorities from evacuating civilians caught up in the battle for the Syrian border town of Kobani, a local official said Friday.
At the same time, Kobani district chief Anwar Muslim, said US-led air strikes had destroyed many Islamic State group vehicles and artillery pieces, and that the town's defenders are reinforcing their positions.
"There are civilians trapped in the centre and south of town, whom we cannot evacuate because of snipers and mortar fire," Muslim told AFP. "Their situation is difficult."
There are no precise figures on how many non-combattants remain in Kobane, also known as Ain al-Arab.
Last week, the United Nations spoke of as many as 700, mostly elderly, civilians being trapped in the centre of the town. Another 10,000-13,000 were said to be gathered near the Turkish border.
For its part, the Britain-based Syrian Observatory for Human Rights says there are hundreds of civilians in the centre and west of town and that many of them refuse to leave, preferring to die than go into exile.