Four Hidden Banshees

During this level when you reach the wooden shack type structure, clear out all the enemies. Have one player stay behind and one player go ahead. Behind a box at the back of the wooden shack (you will need to move it) a switch will appear for a few seconds right after player two activates a hidden switch that is a little further in the level. The hidden switch that player two needs to activate for the first switch to appear is off a small cliff to the left, right before you blow up the covie sniper tower. Once both players activate the switches 4 shiny new Banshees appear near the wooden shack.