Which Boeing aircraft carried the Space Shuttle orbiter on its back between landing sites and launch facilities?

The Boeing 747 Shuttle Carrier Aircraft carried Space Shuttle orbiters between landing sites and launch facilities.

NASA modified two Boeing 747s for this task. One was a Boeing 747-100, and the other was a Boeing 747-100SR, a short-range version originally built for Japan Airlines. Each aircraft received structural modifications and attachment hardware for securing an orbiter above its fuselage.

The Shuttle Carrier Aircraft transported orbiters after landing at Edwards Air Force Base in California when weather or operational requirements prevented an immediate ground return. The aircraft also moved orbiters between NASA facilities and other locations.

The orbiter created substantial aerodynamic drag and added weight, so the carrier aircraft flew at lower altitudes and shorter ranges than normal airline operations. The arrangement was visually dramatic but technically specialized, not a standard passenger configuration.