The pilots who volunteered to fly the D-558-1 Skystreak and the D-558-2 Skyrocket undertook tremendous risks involved in becoming pioneers of flight. Their endeavors made an undeniable contribution to the safety of jet travel. One of those courageous pilots was Douglas company test pilot Gene May. Between 1947 and 1949, May flew more transonic flights than any other pilot. He flew not only the D-558-1 but also the Bell X-1, in which he became the sixth person to break the sound barrier. He retired from flight testing in 1949 after proving the Douglas D558-2 Skyrocket.