Putting it very much simplified, the Stratospheric Observatory for Infrared Astronomy, SOFIA, consists of a German telescope in a NASA aircraft. The 747SP as a platform allows for 10 hour missions typically at 41,000ft or more, above almost all water vapour that would block parts of infrared light. SOFIA was decommissioned the following year, flying its last mission out of Palmdale, CA in the night of 27 and 28 September 2022.