Defeating The Chopper at Stark Towers
When you reach this part of the level, you may be compelled to take the sniper rifle to your left. You can if desired, but it is not required. If you want to get out quick, run to the middle rock near the edge (where the chopper is flying). You will find an anti-tank launcher (rocket launcher) and what may be an unlimited ammo cache. Try to aim for the man with the rocket launcher in the chopper (usually on the right). After you hit him, keep firing missiles at the chopper. Make sure that you strafe (or at least keep moving), as there are snipers in almost all directions around you.