The Space Shuttle orbiter Endeavour passes over KSC's Shuttle Landing Facility atop NASA's Boeing 747 Shuttle carrier Aircraft (SCA) as it returns March 27, 1997 from Palmdale, California, after an eight-month Orbiter Maintenance Down Period (OMDP). Nearly 100 modifications were made to Endeavour during that time period, including some that were directly associated with work required to support International Space Station (ISS) operations. The most extensive of the modifications was the installation of an external airlock to allow the orbiter to dock with the Station. Other modifications included upgrades to Endeavour's power supply system, general purpose computers and thermal protection system, along with the installation of new light-weight commander and pilot seats and other weight-saving modifications.