I don’t think there’s a hard set boundary (I don’t remember that the ‘67 OST defines one). The FAI treats the Karman line as the limit between atmospheric and

I don’t think there’s a hard set boundary (I don’t remember that the ‘67 OST defines one). The FAI treats the Karman line as the limit between atmospheric and space flight. USAF uses a lower 50 miles threshold (80km), NASA uses that for uniformity since 2005.