Optimus Prime gained a jet pack after being upgraded by the Forge of Solus Prime.
After Smokescreen had placed the Forge of Solus Prime on Optimus' right hand, Optimus was resurrected in a new body that came with a built in jet pack. Optimus flew to Darkmount to take on Megatron.
Megatron severley damaged some of Optimus's jet pack with his Dark Star Saber. It appeared to have been repaired before Predacons Rising.
After Optimus sacrificed himself, his jet pack was last seen with him as he flew into the Core of Cybertron.