Although the plane in the film resembles the Bell X-1, a realistic full-scale JA-3/JA-4 model created by Paul Mantz, the aerial sequence director, was built for $15,000. The jet was constructed on the frame of a highly-modified Bell P-39 Airacobra. The Warner Bros contract called for completion of a realistic fighter able to taxi, eject exhaust, and deploy parachutes.
The German jet fighter that is encountered during the B-17 bombing mission is not actual wartime footage of a Messerschmitt Me 163 Komet, it is a model of a rocket-powered interceptor which, at the time, was the fastest aircraft in the world.
In the movie an escape pod was designed into the fictional JA-3/JA-4. However, in 1952, the Bell X-2, an experimental supersonic aircraft capable of going Mach 2 - 3, started flight testing - and this aircraft did incorporate an escape pod, similar to the movie. Unfortunately, like the early part of the movie, the capsule had design deficiencies - it required the pilot to bail out of the capsule after ejection, as opposed to being fully automatic. In the one time it was used, the pilot, Mel Apt, separated from the X-2 successfully, similar to the later part of the movie - but he was apparently knocked unconscious, so he didn't get out of the capsule before it slammed into the desert floor, killing him.
Humphrey Bogart's character was in the 323rd Bomb Squadron that flew out of Bassingbourn Air Base. This base was given to the USAAF (United States Army Air Corps) by the RAF (Royal Air Force) as the first home of the B-17s in the UK. This base was the home of The Memphis Belle and was visited by the royal family on two occasions. Clark Gable even flew out of Bassingbourn once, though he was not stationed here during his tour as a side gunner.
Matt Brennan (Humphrey Bogart) supposedly flew the JA-3 from Nome, AK to Washington National Airport (DCA, now Ronald Reagan Washington National Airport), an estimated distance of 5,300 miles, completing the flight in approximately 4.5 hours - an average speed of nearly 1200 mph. On 6 March 1990, the SR-71 flew from Palmdale, CA (PMD) to Dulles International Airport (IAD) - outside Washington D.C., a distance of 2,299.7 miles in 64 minutes 20 seconds for an average speed of 2,144.8 mph.