When you start the level, go right, then right again, and drop down the first hole that you come across. This is one of the two hangars. The first officer is there (for some strange reason he dies by himself sometimes, so he may not be there). Also, take out the two turrets in the room, which guard either door. Now make your way back up into the vent that you came out of, which is above the door next the stairs with the switch (by the red flashing light). When you reach the top of the vent, head towards the red-tinted area of the vents, which you should be able to see. Take the first left, pass a duct, then fall down the next hole you come across. Fall down again and you'll be in the shower area. Go out of it, turn left, and break the vent guard in the far right corner. Continue down the vent, break the cover at the end, and you're in the mess hall. The second officer is in here. When he's dead, destroy the turret and make your way back through the vent and back into the shower room, then up into the duct ag Head in the direction of the yellow-orange light (not the yellow-blue light) and fall down the hole there. You are now in the second hangar. Go across the room to the door (not the one with the turret) and kill all three marines inside. A predator will then appear behind you in the hangar. Kill him with a couple of charged-up tail slashes to end the level