The Langley Aerodrome A used the first internal combustion engine specifically designed for an aircraft.  The original form built by Stephen M. Balzer was not very reliable and could only run for a few minutes. After it was redesigned and rebuilt as a water-cooled radial by Charles M. Manly, Samuel P. Langley's assistant, it had the best power-to-weight ratio of any engine in the world until 1906 and could run for up to 10 hours.
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