During 13 of the 199 total X-15 flights, eight pilots flew above 264,000 feet or 50 miles, thereby qualifying as astronauts according to the United States definition of the space border.
During 13 of the 199 total X-15 flights, eight pilots flew above 264,000 feet or 50 miles, thereby qualifying as astronauts according to the United States definition of the space border.