Before the Great War between the Autobots and Decepticons broke out, Jetfire was a partner and friend to Starscream. The two were as close as brother; the one as calm, rational and slow to anger as the other was jealous, erratic and arrogant. When Starscream joined the Decepticons in attacking the Autobot held cities of Cybertron. Jetfire was slow to choose sides. He was hesitant to join in the slaughter of largely defenseless Autobots, but did not want to take up arms against someone he'd considered a friend.
When the full extent of the treachery of the Decepticons became clear however, Jetfire joined the Autobots without reservation. The anger he felt as his betrayal by Starscream never waned. He fought his former friend at every turn. The sky over many a battlefield filled with fire as the two master fliers engaged in dog fight after dog fight, neither ever completely destroying the other.