Kármán line

The Kármán line is an internationally recognized boundary about 100 kilometers (62 miles) above Earth's sea level, marking the edge of space. At this altitude, the atmosphere becomes too thin for conventional aircraft to generate enough lift, meaning airplanes can't stay flying there using normal wings. Instead, it's generally considered the point where space begins, where spacecraft and satellites operate, and where the effects of Earth's atmosphere are minimal. While the line isn't physically marked on the sky, it serves as a standard reference for distinguishing between aeronautics and astronautics.