The Stratospheric Observatory For Infrared Astronomy (SOFIA) was based on an commercial airplane, a Boeing 747SP wide-body aircraft. This was then modified to include a large door in the aft fuselage that could be opened in flight to allow a 2.5 m (8.2 ft) diameter reflecting telescope access to the sky. This telescope was designed for infrared astronomy observations in the stratosphere at altitudes of about 13 kilometres (43,000 ft). SOFIA's flight capability allowed it to rise above almost all of the water vapor in the Earth's atmosphere, which blocks some infrared wavelengths from reaching the ground. At the aircraft's cruising altitude, 85% of the full infrared range was available. The aircraft could also travel above almost any point on the Earth's surface, allowing observation from the northern hemispheres.
Observational flights were flown several nights a week. The SOFIA Observatory was based at NASA's Armstrong Flight Research Center at Palmdale Regional Airport, California, while the SOFIA Science Center was based in Ames Research Center, in Mountain View, California.