Kármán Line
The Kármán line is a conventional boundary placed 100 kilometers, or about 62 miles, above mean sea level and widely used to distinguish aeronautical flight from astronautical flight.
Technical meaning
The Fédération Aéronautique Internationale uses the 100-kilometer altitude for astronautical records. The atmosphere does not end abruptly at this altitude, and the line is not a universally binding legal border. Other institutions and national practices have used different thresholds for particular purposes.
Why it matters
The line provides a simple public and record-keeping convention in a domain where the physical transition is gradual and the legal boundary remains unsettled. It appears frequently in discussions of suborbital tourism, astronaut status, flight records, and the edge of space.