Good thing this isn't for "any" aircraft, or all the experimental fighters and bombers would take up pages and pages of space.
I'm going to nominate the Avro Canada Jetliner, just for the sake of mentioning it. Taken from: http://www.avroland.ca/al-c102.shtml
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Photo © Pierre Lacombe
"The first prototype, CF-EJD-X christened the Jetliner, first flew 10 August 1949, just 25 months after the design of the Derwent-engined verstion was started! The crew consitited of Avro UK Chief test pilot Jimmy Orrel; Avro Canada Chief Test Pilot Don Rogers; and flight engineer Bill Baker. The first flight was without any problems and the only problem in over 500 hours of flight occured on the second flight (16 August 1949) when the aircraft had to make an emergency belly-landing because the main gear would not extend (the damage was so minor that the aircraft was flying within three weeks).
By December 1950 the Jetliner had reached 39,800 feet and had exceeded 500 mph in level flight!
Howard Hughes was so impressed with the Jetliner that he wanted to manufacture it under license at Convair and using it on TWA routes, but the U.S. government would not agree to Convair devoting effort and spce to a civil project in view of the Korean crisis.
The Jetliner never did go into comercial use but was used as the aerial survey & photo platform for the CF-100 project, as orders were never placed, construction on the partially built secont prototype was abandoned. On 10 December 1956 the Jetliner was ordered distroyed, and after contacting the National Aviation Museum turned up no interest in obtaining the aircraft due to a lack of space, the Jetliner was cut up on the 13th of December 1956 with only the cockpit section surviving (in the Canadian Aviation Museum in Ottawa)."