I sent 2 fighters to intercept a pack of 3 and decided to tail them. Then the pack of alien fighters shot down my crew ship. Immediately after I closed the report that showed the casualties the airfight minigame showed and no matter how many times I retreated the mini game would restart.
I don't know if the shooting of my dropship had anything to do or the number of alien ships (I didn't try to retreat 6 times - 2 aircrafts x 3 alien fighters).