The jet that trained the astronauts
For the last three decades, NASA has operated a small number of T-38s to help train future space-goers in pilot proficiency and training. Although the conditions they would face flying the T-38 were not identical to those they would encounter flying the shuttle, astronaut pilots were put through rigorous training missions with the craft and forced to react to real-world scenarios to help them prepare for the unexpected. The twin-engine supersonic jet trainer helped the astronauts with a myriad number of situational awareness and emergency training exercises - some where they were put into positions where their lives depended upon getting things right in a hurry.
It's actually our most important training that we do as astronauts," said Terry Virts, who flew as the pilot of STS-130 aboard shuttle Endeavour. "It's the one place where we're not in a simulator. It's real flying and if you make a mistake, you can get hurt or break something or run out of gas. There are a lot of things that happen real-world in a T-38 that don't happen in the simulator."
In earlier shuttle landings, T-38 chase pilots followed the shuttle down to a runway, updating shuttle crews about the condition of the spacecraft and what to expect in the approach. They also could mirror the shuttle all the way through its approach on a glide path that is seven times steeper than an airliner's.