What altitude boundary do the United States Air Force and NASA historically use for astronaut wings?

50 miles (approximately 80 kilometers) above sea level

While the 100-kilometer mark is the global standard set by the FAI, specific national agencies use different metrics based on their operational mandates or established historical precedents. Both the United States Air Force and NASA have traditionally recognized a slightly lower altitude of 50 miles, which equates to approximately 80 kilometers above sea level, as the demarcation for designating an individual as an astronaut. This difference illustrates that while the underlying science is shared, the formal labeling and internal certification standards for crossing into space can vary between international convention and specific national agencies.