During astronaut training, Sullivan reached 63,000 feet in a NASA WB-57F, an unofficial sustained U.S. women's altitude record.
On July 1, 1979, while training as a NASA astronaut candidate, Kathryn Sullivan flew aboard a NASA WB-57F high-altitude reconnaissance aircraft and reached a sustained altitude of approximately 63,000 feet (19,000 meters) during a four-hour flight. This feat set an unofficial sustained American aviation altitude record for women.
The flight demonstrated Sullivan's aptitude not only for scientific work but also for the physically demanding, high-performance flying that characterized much of astronaut training in the late 1970s. At the time, women were still a rarity in high-altitude and military test-flight programs, and achievements like this helped normalize women's participation in cutting-edge aviation and aerospace roles.
Though the record was never formally ratified by an official aviation body—hence its designation as 'unofficial'—it stood as an early marker of Sullivan's exceptional capabilities as a member of NASA's first astronaut class to include women (Astronaut Group 8, selected in 1978). It also foreshadowed her later distinctions in both space exploration and deep-sea exploration, cementing a career defined by pushing the boundaries of where humans could safely and successfully venture.