Military aircraft UHF radios usually transmit with about 20-30 watts, and are often VERY EASY to hear from dozens, sometimes hundreds, of miles away depending on the altitude they're flying at & what sort of receiver/antenna setup you have, etc. You don't need a massive antenna or special receiver to hear them, but having a positive mindset & not "giving-up" usually helps, just like it does with most other things in life.
From my home, I hear aircraft as they're on their final approach to Nellis AFB, which is over 100 air-miles away & with a mountain range or two in-between me & it, and since the aircraft are on final, they're only a couple thousand feet up in the air. I do have numerous specialized antennas made for 225-400MHz, but even with my Uniden BC-396XT handheld in the car, I can hear air/air stuff taking place in the Nevada Test & Training Range, using the handheld's stock antenna 100+ miles away, & with at least one mountain range in-between them & I.
Hill AFB has a decent amount of flight activity, plus as someone else mentioned, there's the huge Utah Test & Training Range military operating area with lots of aviation & ground activity.
Search 138-144MHz & 148-150.8MHz in AM mode, 25kHz steps, and search 225-400MHz also in AM mode & 25kHz steps. That'll get you off to a good start. Eventually you might want to get an antenna designed for that freq range, and also search 30-88MHz for tactical air/air & air/ground activity, etc.