The Northrop T-38 was used by the Air Force as a two-seat, supersonic trainer and was used by NASA's research pilots for proficiency and mission support flights. With its lower fuel burn rate and maintenance costs, the T-38 is cheaper to operate than the larger and faster F-18.
This is the model plane that you always saw escort the shuttle each time it returned to earth. In Houston, we saw many of the astronauts return to Ellington Field after their missions flying these. It's a plane that isn't large, but looks like it would be a lot of fun to fly. I'm available if anyone takes one up soon.