Unless you are part of the crew, or you "hitch" a flight on one while on leave. Though I can definitely understand not wanting to fly on one again. I did fly on a couple of interesting aircraft in the Air Force, such as a C-5 (has an upper deck with passenger area, seats face backwards) and a smaller Fokker cargo plane.

For official travel, since I wasn't part of any aircraft crew, I either flew commercial or on a chartered flight (both times on 747s).