The Kármán line is an established boundary that separates Earth's atmosphere from outer space, as determined by the Fédération aéronautique internationale (FAI). This boundary is important for legal and regulatory purposes, as aircraft and spacecraft fall under different jurisdictions and are subject to different treaties. The FAI has set the boundary of space to begin 100 kilometers above Earth's sea level, which is beyond the reach of regular airplanes and where satellites begin to decay before completing an orbit. The line is named after Theodore von Kármán, a renowned engineer and physicist known for his contributions in aeronautics and astronautics. While different countries and entities have their own boundary definitions for space, the majority of regulatory agencies accept the FAI's Kármán line definition or something close to it.