How to Find CortanaEdit
Starting from the AA missile (opposite end of the beach), go straight. At your left side, there should be an old half-destroyed bunker with a hole in the side. Go through the hole. Turn right, and a computer should be laying on a desk. Go to the computer, look at the computer screen that shows a picture of the hangar from the mission Crows Nest.
Look at this screen for a while. Eventually, an image of Cortana should appear on the screen for a split second, and then disappear. The image reappears on the screen roughly every two minutes.