Where does space begin?As we said, space is the area above the Earth's atmosphere. However, there is no specific boundary because the atmosphere gradually thins as you move away from the Earth and you can find traces of the gasses we breathe over 100 miles above the earth. In contrast, most passenger jets fly around only 30,000 feet (5.7 miles). Even the best military jets rarely climb above 100,000 feet (a little less than 19 miles).
NASA awards astronaut status to anyone who flies above 50 miles in altitude. Others people may have differing ideas based on their own parameters.