More info on the Learjet
The first Learjet was the Model 23. If I remember correctly, Bill Lear's son was involved in the design of a Swiss fighter called the P-16. The P-16 was cancelled but Lear found the wing suitable for his idea of a small business jet.
I don't remember for certain, but a specific Model 23 has been used in quite a few movies including "Capricorn One" where it did some aggressive flying. That may have been the plane used in that particular episode of "JAG", although it also appears they used a computer model at some points in the flight.