SOPHIA isn't a 747-400; if it was, it would probably still be flying. Instead, it's the now-extremely-rare 747SP, a 747-100 derivative designed for special long

SOPHIA isn't a 747-400; if it was, it would probably still be flying. Instead, it's the now-extremely-rare 747SP, a 747-100 derivative designed for special long range operations: https://en.wikipedia.org/wiki/Boeing_747SP https://en.wikipedia.org/wiki/Boeing_747SP The original 747-100 had a much shorter range than the 747-400 (due to earlier, fuel-thirsty engines and a bunch of other early design decisions). The SP was shortened and modified extensively to achieve roughly the range of the -400, albeit with fewer passengers, but was obsolescent by the early 1980s. SOFIA was built into an aircraft that first flew in 1977: today it's a 45-year old example of a plane with a 30 year design life, and unlike the B-52 there is no deep-pocket Pentagon contract paying for long-term maintenance. (Yes, putting her out to pasture in an aviation museum would be the ideal fate for this historic aircraft.) https://en.wikipedia.org/wiki/Stratospheric_Observatory_for_Infrared_Astronomy#The_SOFIA_aircraft https://en.wikipedia.org/wiki/Stratospheric_Observatory_for_...