Near space is the region of Earth's atmosphere that lies between 20 to 100 km (65,000 and 328,000 feet) above sea level, encompassing the stratosphere, mesosphere, and the lower thermosphere. It extends roughly from the Armstrong limit above which humans need a pressure suit to survive, up to the Kármán line where astrodynamics must take over from aerodynamics in order to achieve flight. Thus, near space is above where commercial airliners fly but below orbiting satellites.