It was plain at once that new principles of engine construction must be adopted before a motor could be designed of high power yet light enough to be borne in the slender body of an airplane.

The internal combustion engine had now come into use.

Langley went to Europe in 1900, seeking his motor, only to be told that what he sought was impossible.
His assistant, Charles M.Manly, meanwhile found a builder of engines in America who was willing to make the attempt.

But, after two years of waiting for it, the engine proved a failure.

Manly then had the several parts of it, which he deemed hopeful, transported to Washington, and there at the Smithsonian Institution he labored and experimented until he evolved a light and powerful gasoline motor.