On This Day in History / March 7, 2023 1961: Major Robert M. White pilots the North American X-15 hypersonic research airplane to a speed of 2,905 miles per hour. In accomplishing this, White becomes the first man to exceed Mach 4 during this mission. In July the following year, White will become the first to fly into space under the aircraft’s own power and return to the Earth to a safe landing. (USAF Art Program)