Ace London was an extremely egotistical, attention-starved wolf who was an old childhood rival of Baloo's. A stunt pilot, Ace London's exceptional piloting skills were often called on by various organizations, including the military, to test out new kinds of planes and plane engines. When the Air Force invented an experimental jet engine, General Patton, an admirer of Ace's supposedly "heroic" exploits, not only recruited Ace to test the engine out, but also entrusted to him the task of picking up the crate containing the engine from Sally's Alley, to be flown safely to the testing grounds somewhere outside of Cape Suzette.
Unfortunately for the Air Force, Ace proved to be a complete imbecile. He and his two equally thickheaded and inattentive wingmen/groupies grabbed Baloo's crate by mistake: Instead of a jet engine, General Patton and the Air Force's scientists got a crateload of pickles. To save face, Ace lied and said that he didn't grab the wrong crate; rather, Baloo had switched them and stolen the engine. Furious, Patton gave Ace one chance to recover the "stolen" engine, or else. Driven by desperation, Ace did everything he could to try and get it back. This included firing on the Sea Duck unprovoked, despite the advice from his wingmen that this was against the rules of engagement.
After several chases and at least two run-ins with Don Karnage and the Sky Pirates (who also wanted the engine), Ace failed to reclaim the engine. Baloo and Wildcat used it to escape from him and the pirates, breaking the sound barrier and thoroughly impressing General Patton. As for Ace, his wingmen, disillusioned with their idol's unheroic behavior, informed General Patton of how he had shot at the Sea Duck. As this violated the rules of engagement, an enraged Patton punished Ace (and simultaneously thanked Baloo) by forcing him to deliver Baloo's shipment of pickles.