In the level Assault on the Control Room there is a Banshee that you can get earlier than you are supposed to be able to. When you come out of the main building and find the marines that are 'pinned down', kill the enemies and pick up the rocket launcher and the sniper rifle (not required but makes this a bit easier). Walk/Drive to the next area (the one with the pelican that has crashed) and kill the enemies. Keep going along the frozen river but before you start going down a slant, look up. You should see a platform. The banshee is on it. With the sniper rifle (if you brought it) aim roughly in the middle of the platform (between the support arm thingie and the front). Switch to your rocket launcher and fire. You should have hit the area that you were aiming at with your SR. Switch back to your SR and zoom in and look at the front of the platform. If you did this right you should see the banshee falling from the platform it should land somewhere near the rocks in the corner. If it doesn't fall, then go back and get the tank then go through the tunnel and go onto the elevated part of land just outside the exit with the shades on it. Park the tank on the right side and get out. If you fall off the elevated part, DON'T GO NEAR THE POND. If you do, you'll get a checkpoint and the elite guarding that banshee will fly off with it. Okay... so anyways, when you get out of the tank jump onto the top if you're having trouble jump onto the tread covers and then 'double jump' onto the top (jump and press in the left analog stick and the height of your jump). When you're on use your SR and look at the platform. If you see the top of the banshee, then that means you can go try to get it down again. If not then you must Revert to Saved and try again, if you want to. When you get it, you'll... er... have it. So uh.. yeah... congrats.