High altitude passenger plane. Computer artwork of a passenger plane flying above the stratosphere. At this height, passengers are able to view the curvature of the Earth and the darkness of space. Aircraft are also able to fly faster and reduce travelling times between destinations due to reduced friction in the thinner atmosphere. Most commercial passenger planes fly at an altitude between 6,000 and 12,000 metres. Spyplanes such as the U-2 and SR-71 Blackbird are able to fly above 21,000 metres. The Earth's stratosphere extends to 50,000 metres.