I'm reposting this from the events thread because this seems like a better spot. A mod can delete my other post if they want.
I uploaded the results of our experimentation today on The Package into my fileshare, the gamertag being "DrKevoun"
We performed the banshee spawn trick as detailed in the video guides that people have posted and then flew around for about 45 minutes before finding something odd. After crashing my banshee somewhere outside the map, I respawned onto Enigma's location while he was flying around. Apparently there is an invisible 'floor' in the air the banshee can't go through that we were able to walk around on. The location of the area we discovered this is in "Weird Banshee Spawn". In this clip I spawn in the air, and then enigma circles back around and lands his banshee there.
In the second clip, "Weird Banshee Spawn 2," we walk through a 'wall' of fire that Enigma claimed is impossible to go through in the banshee, and quickly start gaining elevation. We discovered that this walking area extends pretty far in most directions, but there are also pitfalls etc. to fall into.
In the third clip, "Mountainwalk," I filmed a few different areas accessible after landing. Enigma went pretty much straight north, where the floor begins to descend fairly rapidly. I walked back toward the playing area and find myself on top of the burning building. I also found places where you can walk around on top of the mountains as if they are solid, which I think would be a good area to search for switches etc. You might be able to fly banshees directly to these mountains and land on them even with the boundaries negated. I would advise killing off all of the enemies on the map before exploring because I was blown up by a fuel rod turret.
For reference, we were playing on legendary and destroyed the two AA guns before performing the trick. Also, we had three players in the game.
I don't really know how to render videos or post them in any other way so if someone could capture some video or screenshots that might be nice for reference.