It seems to be established (particularly late) in the G1 series that Autobots can't fly. But yet in the pilot and several season 1 episodes, they could. They were flying when they first met Spike and Sparkplug, rescuing them from the oil rig when the Decepticons attacked. Ironhide flew when he launches an attack on Skywarp. The Dinobots certainly flew just before they were first used to rescue the majority of the Autobots. Wheeljack flies to aid Skyfire when the Insecticons made their first appearance. These are among several examples of Autobots being able to fly. But from season 2 on, they would only be seen flying if they were wearing rocket packs, like when they went to Dinobot Island. Frankly, I would have liked for one episode where Optimus Prime in vehicle mode would say "Autobots, transform and fly out!"