Part II : 1950-1957
 In 1953, military aviation was in transition from subsonic to supersonic flight. Chance-Vought delivered the last propeller-driven fighter, an F4U Corsair, to the Navy in February. Three months later, the YF-100A, produced by North American Aviation for the Air Force, became the first service supersonic fighter-the start of the Century series. These were made possible by more powerful turbojet engines such as the Pratt & Whitney J-57, which went into production in 1953. Speed, however, is but one of the familiar trinity of major military aviation goals-higher, faster, farther. Higher altitudes meant less vulnerability for bombers and reconnaissance aircraft. The altitude goal frequently mentioned during the period was 30 500 meters. Greater range was not neglected as a goal, but global bases and in-flight refueling sometimes made it possible to compromise range in favor of other goals. In addition, military aviation planners during the 1950s felt the keen competition of guided missiles, which were in rapid ascendancy. The rivalry between aviation and missile men was strong.
From late 1952 to early 1954, three men of diverse backgrounds initiated proposals for achieving flight at very high altitudes. One was an Air Force major stationed at Wright Field, John D. Seaberg; another was a famous airplane designer, Clarence L. (Kelly) Johnson of Lockheed Aircraft; and the third was a lone British inventor with a novel idea, Randolph Rae. These initiatives and the activities they generated proceeded concurrently with, but largely independent of, the NACA research described in the previous chapter. The initiative of Seaberg led to the new altitude capability of the B-57; Johnson's led to the extraordinary U-2 high-altitude reconnaissance airplane; and Rae's led to his personal disillusionment, but new interest within the Air Force for using liquid hydrogen in aircraft.