You know that one screenshot that shows the Master Cheif flying around in a Banshee in the large cavern on Rolling Thunder which contains one intact bridge and one blown out bridge? As it turns out, you don't have to have some special developer build of Halo to do it. You just need a rocket launcher, pixel vision, and a bit of luck.
Just after the point where you are forced to abandon the Scorpion tank because the cave through which you must travel will not let you pass, you and your marines engage a sizeable group of Cevenant armed with stationary guns, a couple of ghosts, and one banshee. The typical approach to this situation might be to pick off all of the grunts with the sniper rifle you no doubt have with you followed by charging in to mop up those mechanized units (plus one airborn) with that SSM launcher.
Well, if you have just a tad of discretion and hug yourself against the edge of the cliff you climb up, you can position yourself against a tree for a good look across the canyon. Zooming in with the SPNKR, you might notice the faint outline of a banshee past the large sunken covered structure. If you are careful enough, its pilot hasn't caught on to your presence and taken to the air to deliver some tasy white-hot plasma bolts followed up by a healthy dose of neon green fuel-rod surpise. I figured since I had the bastard in my sights anyway, I would let loose a rocket in an attempt to keep the skies clear as my marines charged up the cliff face. Turns out he never sees it coming. In one blast, the empty banshee goes flying and lands upside down thus rendering it completely useless. Useless, that is, to the covenant. Fortunately, our Master Chief has more than enough muscle to flip over a flimsly little flying contraption like a banshee.
I was now able to fly around the mojority of the level with impunity. I could even make it all the way back to where we first encounter fire team Zulu. I could also skip a rather large portion of the map by flying strait up onto the walkways above. Unfortunately, a necessary door remains locked unless you backtrack enough to activate some enemies. A small price to pay, IMO, for the time savings.