There is no formal definition for the end of the atmosphere and the beginning of space, but an altitude can be arbitrarily chosen. A common choice is the Kármán Line which is an altitude of 100km. But 101km above would still have low amounts of atmosphere in it and I wouldn't consider it in space if it stays near the earth.

The link states that the Kármán Line is well above the altitude that traditional aircraft are able to fly at.