The widely recognised boundary is the Kármán line, which lies at an altitude of 100 kilometres (about 62 miles) above sea level. It marks the conventional border between Earth's atmosphere and outer space, used by aviation and aerospace bodies as the dividing line between aircraft and spacecraft territory.

The Kármán line is the boundary between Earth's atmosphere and outer space, set at 100 km (62 mi) altitude. Above it, the air is too thin for conventional aircraft to generate lift, so an object must travel at orbital speed to stay aloft. It is the standard definition of where space begins.

A fighter jet like the MiG-29 can climb to around 17–19 km on an Edge of Space flight — high in the stratosphere but still far below the 100 km Kármán line. From that altitude you can see the curvature of the Earth and a darkening sky, the closest a MiG-29 experience gets to true space.

Not in level flight — but people have fallen from near it. Daredevils have ridden balloons to the stratosphere and jumped from the edge of space, free-falling back through the atmosphere. Reaching orbital space itself, however, still requires a rocket to achieve the necessary speed and altitude.

Above about 100 km the atmosphere is so thin that wings can no longer generate meaningful lift, no matter how fast a plane flies. To stay up beyond that point an object must move at orbital velocity, which is the realm of spacecraft. That physical limit is why the Kármán line defines the edge of space.