The Syrian Observatory for Human Rights (SOHR) is reporting that the Islamic State has at least three captured MiGs and is yraining pilots to fly them. A report in The Guardian here and at the SOHR website here. The report claims that three aircraft, believed to be MiG-21s or MiG-23s, have been seen flying from the al-Jarrah air base east of Aleppo. The base is controlled by ISIS, which also has control of other Syrian air bases. The report says the pilots are being trained by former pilots of the Iraqi Air Force in the Saddam era.
There are also reports that the Israeli Air Force has raised its alert level.