There is another post sort of like this, but it takes two people, and this only takes one. In the level Metropolis, take the tank and destroy all the enemies on the bridge and the wraiths except for one banshee. Make sure your marines are dead so they don't take it out. after you take out the Wraiths by the tunnel, get on top of your tank, on top of the part that shoots, and then wait for the banshee(it will keep on circling and diving) Right when it gets to it's lowest point, jump up and for a split second, not even half a second, there will be a window of time for you to take over the banshee. After you get in you will be sent flying backwards with no control, and then it will stop. Get out and use the tank to take out everyone in the first part of the tunnel. Then go back to your banshee with the tank. VERY CAREFULLY push the banshee very very slowly with the tank into the tunnel. It's really important that you don't rush it, or it will explode. Also try not to get on top of it. Once you get further into the tunnel, get in the banshee and fly straight to the third oart of the tunnel with turbo on. take out everyone in that section. Now, even more carefully, shoot off the banshee's wings with the battle rifle so it will fit through the tunnel. As soon as you leave the tunnel, fly straight up, and you will see two buildings with a bridge connecting them. In the middle of the bridge there will be a turret that looks like a plasma turret, but it's actually a scarab gun. Enjoy!