They swap between their Cybertronian jet modes and their robot modes, where they could also hover in the air. Though relatively weak as combatants, Fliers attack in large groups to make up for it in battle.
The Autobot (and Neutral) Fliers were called "Aerialbots" by the Decepticon troopers while the Decepticon Fliers were called "Seekers" by the Autobot infantry.
After the Great Exodus, no Autobot fliers were seen, though they are still alive. The Decepticon fliers are intact with Megatron.
The Decepticon fliers then got a new paint job of black and white. Optimus Prime was able to fly with his jet pack in his new mode.