Remember you need the sputnik skull to do this.

To exit this, kill yourself or pause the game and revert to last checkpoint. When you press it it will keep fliping for a while.if you see anyone who survived, kill them and their body will float as well as their gun. If u go near the pelican, it will say,hold x to flip banshee(weird isnt it?). Somehow, when it crashes you will still be alive, floating above water. You ride it untill it crashes into some water. As soon as the marines get off the pelican (except the gunner)hold x (there wont be a message telling you to hold x). Destroy the two wraiths and ghosts.near the wraiths are stairs.go up them and wait till a pelican arrives. First,get to the part where you must save the marines trapped inside the building. In the level metropolis, you can ride in the pelican,(getting the sputnik skull is required). Your previous weapons will not, however, hover and shoot like the SMGs you swap. The gun fires throughout the entire length of the cut scene. You can also juggle the weapon toward/through the door and have it shoot at you in the cut scene if you so choose. It only has one clip, so after a few seconds of it firing you just hear the trigger being pulled. As you walk toward epicenter of the sound вЂ“ the door leading toward the centre of the Library where the Index/Sacred Icon is found вЂ“ you will see two SMGs floating in midair and firing вЂ“ does this remind anyone of the level 343 Guilty Spark in Halo? You can 'Hold X to swap' and the gun(s) will continue to fire in your hand. As you near the exit of the gondola, and begin to enter the Library where you find a dead human you hear the static sound вЂ“ the sound of SMGs firing.

Halo 2 co op