Staff Writer (Updated: 4/28/2016):
The development of the turbojet originated from multiple sources before it was to become a proven powerplant concerning military aircraft. In Britain, Royal Air Force officer Frank Whittle was convinced of its merits as early as the 1920s and filed a patent for his creation in 1930. Little interest within the British military and industrial ranks meant that his idea lay dormant until a pair of ex-RAF colleagues provided funding for the venture in 1936. At the same time, German engineers were hard at work on their own, separate turbojet design culminating in the first flight of a jet-powered aircraft on August 27th, 1939 - this attributed to the history-making Heinkel He 178 (detailed elsewhere on this site). The British followed on May 15th, 1941 at which point World War 2 (1939-1945) was in full swing.
Before the World War arrived, even American military minds and industry were lukewarm to the idea of jet-powered military platforms - they believing it as something more of science fiction than a tangible solution. With reports emerging from Britain and Germany on advancements made in the field, the American government finally took interest and sent a detachment to England during April of 1941. U.S. General Hap Arnold himself witnessed the British Gloster E.28/39 jet aircraft conduct a series of successful hops and was convinced that "aircraft flying without propellers" was the wave of the future. This led to the two nations - now Allies in the war effort against German - to sign a formal technology agreement in September 1941 to further jet-powered flight equally - the British would supply the original Whittle design work and the Americans were to provide their industry know-how in bringing the engine to mass production. The Whittle turbojet plans were passed on to General Electric to be built in fifteen examples. This would coincide with three test aircraft being designed and built to house the new engines.
For the airframe the charge of its design fell to Bell Aircraft who did not have the fighter production commitments that its rivals had at the time. It also proved itself earlier, to the United States Army Air Forces (USAAF), that it was a forward-thinking aircraft manufacturer through such designs as the P-39 "Aircobra" (with its rear-mounted engine installation and tricycle undercarriage) and the wholly-unique and utterly ambitious YFM-1 "Airacuda" bomber destroyer. While both were inherently limited designs - the Airacobra found modest success in the hands of Soviet pilots via Lend-Lease and the Airacuda - introduced in 1940 - saw only thirteen of its kind built and was retired as early as 1942 - the company was ready to meet the demands of the new project. It had also completed a new facility in New York within reach of the General Electric plant intended to develop the Whittle engine.
A veil of absolute secrecy was established between the USAAF, Bell, and General Electric to the point that the fighter was given a prop-minded designation - "XP-59". Similarly, the engine carried the designation of "Type I-A" to showcase it as nothing more than a General Electric turbosupercharger. Expediency was the call of the day and, within two weeks, the small group of engineers working out of an abandoned factory returned with a scale model of the new fighter. It was based on an original prop-driven, twin-boom design relying on a "pusher" arrangement that company engineers had penciled before the XP-59 program was envisioned (the smaller XP-52). The aircraft was assigned the internal company designation of "Model 27" and an in-house Bell competition settled on the name "Airacomet" in keeping with the company's traditional "Aira-" naming convention.
The Whittle engine made its way - again under secrecy - to the United States from Britain in the hold of a Consolidated B-24 "Liberator" heavy bomber. The included plans were deemed very basic and General Electric engineers were given the green-light to modify it as seen fit. The engine ran for the first time on March 18th, 1942 and outputted 1,250lb of thrust. Lingering issues allowed time for Frank Whittle to journey to the United States and offer his support in streamlining the turbojet.