ISIS itself is its own group of military. In order to have an air force like many countries do, one would need to divide their group so that they could run the air force. Besides needing the equipment like helicopters and airplanes, an air force would also need experts to control these air craft vehicles. Therefore, ISIS does not have its own air force. ISIS has not taken over an air base which it wanted to do by getting the air planes and other air vehicles that are there.
At one time, the base was under heavy fire in order for ISIS to try to take over this important air base in Iraq. However, it is believed that even if ISIS gained and took control of the air base, they would not know how to fly the planes.