The number 747 is so ubiquitous, having adorned the sides of so many aircraft over the decades, that it has become almost synonymous with the jet airliner. Some 3.5 billion people have flown on 747s, according to Boeing, which has manufactured more than 1,400 since the first 747-100 left the factory in 1968.
But not all 747s wound up in regular passenger or cargo service. Today, for instance, one of NASA’s two Shuttle Carrier Aircraft is ferrying the retired space shuttle Endeavour to Los Angeles for display in a museum. Another NASA-owned 747 cruises the skies with an open payload bay, exposing a giant infrared telescope to the heavens. Other aircraft of the same lineage can help fight fires, shoot down missiles or serve as a command center for U.S. government VIPs in the case of nuclear attack or other catastrophe.