Andy Bush comparing the TF-104G with the F-104G:
The TF carried less internal fuel. We used it in the weapons school for introductory rides...where we verified the student's basic flying skills before turning him loose to fly the single seat model. For example, when starting the air-to-air phase, we wanted to expose the student to both high speed and slow speed flight. The plan was to enter a 30 degree dive from about 20000' and accelerate to as fast as the jet would go...we would level off at about 5000' and then point the jet straight up and let it run out of speed. It wasn't unusual to have the students be apprehensive about flying at high speed and they were particularly wary of very slow speeds (too many accidents in Germany).
In the dive, we could get the TF out to about 750KIAS...the TF had more drag than the single seat version because of the canopy. I'd sit in the back and "help" the student stay in the dive until the jet quit accelerating...and then I'd "help" him pull it straight up. I'd make sure he kept the stick neutral until we simply ran out of airspeed...the jet would then flop over and start back downhill. I'd guard the controls again to make sure the guy up front had it under control. All of this was usually accompanied by some heavy breathing from up front!! I used to call this the "Oh ye of little faith" sortie.
Other than no gun and a shorter endurance, the TF was quite similar in performance to the F model.