by Frank P.
Before the Space Shuttle flew its first approach and landing test off the back of a Boeing 747 Carrier, Lockheed, working with NASA, built a full set of Shuttle orbiter avionics in a facility in Houston called the Shuttle Avionics Integration Laboratory (SAIL). Lockheed engineers also conducted tests of all the other orbiter systems that were simulated in the SAIL. When certified, the SAIL was used to check out the orbiter flight software prior to both the approach and landing test and later the first orbital mission, STS-1.
The SAIL served throughout the Shuttle program as a facility where the avionics and software for each mission could be tested and verified prior to the actual mission. It served also as a facility where anomalies that occurred in flight could be simulated on the ground with actual orbiter avionics to provide real-time problem resolutions.