The Bristol 188 was the first Bristol turbojet aeroplane to be built. Two flying examples were constructed with the objective of reaching and sustaining twice the speed of sound for long enough to enable steady-state kinetic heating effects on the structure to be experienced and recorded. After considerable production delays the first aircraft XF923, made its maiden flight 14 April 1962. First flight of XF926,from Filton ,was 29 April 1963. Both aircraft were grounded indefinitely and the project suspended in February 1964, partly due to problems of high fuel consumption and the inability to reach sustained high speed and achieving the original operational requirement for the project.