Dear, Vector Prime.
Could you tell us about Seeker-body Jetfire?
Dear Sky Seeker,
Variations on this individual crop up all across the multiverse, under different names. The Jetfire I am familiar with was a famous explorer, celebrated for defeating the Star Seekers of the Blot Nebula. On one of his expeditions, he tracked the apocryphal AllSpark to a primitive Earth, only to discover to his dismay that the artefact's energon radiation interfered with his telemetry, causing him to crash-land on the North Pole. Unearthed millions of years later, he quickly upgraded himself into a new form with an external booster unit to improve his atmospheric flight capabilities and prevent a similar mishap occurring in future.
In another universe, this was the ex-Omnicon Skyblast, who felt a lack of purpose after the development of Cyber Key technology finally gave the Autobots the ability to boost their own power without relying on others. With his comrades no longer needing his abilities, he upgraded himself into a new Cyber Key-carrying form that would let him do for himself what he had done for them.
And in a negative-polarity universe you might be familiar with, this was none other than Starscream, back when he was a student at the Crystal City Science Institute. Optimus Prime captured him and branded him with an Autobot insignia, but Starscream flatly refused to help the bot who had leveled Crystal City before his very optics, and Prime threw him in a cell to rot—from which he was eventually rescued by Megatron, who had pioneered the art of transformation. Starscream took this innovation and helped develop yet more complex transformations, upgrading himself several times over the ages to meet the demands of an ever-escalating war.