I believe in todays airforce, they teach you to fly right handed, if your going to be in a fighter. It just really depends on the plane u are flying. Cargo planes I don't it matters, bombers same thing, but for fighters like the F16 which has the joystick to the right side of the cockpit, I think you'll have to learn to fly right handed. Im lefty, and wanting to join the airforce, so I don't know. I don't think they will say NO! to you if you wanted to join and you were a lefty. They would teach you to fly right handed with flight simulators most likley until u are ready to fly a real plane right handed. I believe its more on each type of aircraft you will be flying.
F-16 cockpit-Notice the joystick is on the right side of the cockpit.
F-15 cockpit-Notice that the joystick is between the legs, but its right handed.
F-22 cockpit (Not a real one, because there cockpit is top secert, but is what it kinda looks like)- Notice the joystick is to the right just like the F-16
B-52 cockpit-Notice its not a joystick, but its like a steering wheel. (Common for most heavy aircraft)
Blackhawk cockpit-Still right handed.
I really think being left handed and joining the airforce, or army airforce, might matter, just depending on what type of aircraft you will be flying, by the means of bomber, cargo, fighter jet, or helocaptor.