When facing the helicopter as Ghost, focus Run across the room to where the wall starts to curve. Back up against the wall facing the away from the large glass window. Hold AUTO AIM and when the SWAT starts to jump down through the window, use your Focus and dispatch them with as minimal ammo possible. Go back to where you were against the wall earlier and wait for the helicopter to pass over. When it does, it will shoot the wall. If you are in the correct location, it will not hit you. After hearing the bullets stop, run around the wall and the helicopter will be exposed without any protection. Use your Focus and dump at least a clip into it. Then, return to the wall and repeat the process. It only takes three to four times to take down the helicopter.
While playing as Ghost and after shooting off the plane's tire, you will encounter the Agent chopper. Change your weapon from the M95 Sniper Rifle to the SG - 552. Quickly stand almost as far back as you can go from your current position, so that you are not too close to where the chopper will appear. As soon as you see it, use Focus and fire at the same time. The chopper should take major damage, but will leave your health at a minimum of about 20% before backing off. It will then try attacking you from the right; turn about 90 degrees to your right and get ready to blast it with the remaining ammunition. Avoid staying too far back because your shots may have less chance of hitting. You may get killed here if your reflexes are not fast enough. Also, if you defeat the chopper you may be left with just 1% health, but this is enough to get you out of there, let you save your game, and continue the war to save Zion.
To easily defeat both helicopters in The Airport, drop weapons at the ticket counter just before you meet the first helicopter. Using Ghost, under the hard difficulty setting, you can hack and view the map for The Airport, which shows the code PNSRZ10. Use the "DROP" command with that code and get two M240 weapons at the ticket counter just before the first helicopter battle. Using an M240 takes about eight seconds to kill a helicopter. For the first helicopter, wait behind a wall for it to turn around after firing, then run out to unload on it. It should go down before it makes its way to the roof to drop cops through the window. As for the second helicopter, hide behind the columns in the tower and use the "FOCUS" and "STRAFE" commands to shoot at it and still keep moving towards the opposite column. It may take about three times if you follow this method with the M240. The tough part about using the M240 is remembering not to waste it in the time between the two helicopter battles.
It is easier to kill the first helicopter by allowing it to make its first pass. While it passes, prepare an automatic weapon. As soon as the shooting stops, press FOCUS, get around the corner, and start to shoot the helicopter. Follow it all the way, You should get about three clips unloaded at the helicopter and will almost always kill it in its first pass. If done correctly, this allows you to destroy the helicopter without a scratch. Remember to get away from the right side of the window when the helicopter starts to fall or the explosion will kill you.
When facing the Agent helicopter, immediately use the SSG-552 quickly. When the helicopter appears, shoot it as quickly as possible and he will die. Run down the stairs or you will also die. Note: This doesn't work all the time.
This strategy is easy but time consuming. Once the mission begins, use Focus and run to the wall opposite to you. Wait for the SWAT members to pop in from the roof. Make sure you have stun grenades and the machine gun. Having flash bangs is also recommended. Kill the SWAT members using Focus to avoid damage and steal their ammunition. To take them out, once they pop in tossa grenade at them, then mow them down with the machine gun. Then, hide behind the fountain and wait for the helicopter to pass. It will be shooting a high powered chain gun. It will soon turn around with its closed side to you and be vulnerable. Use Focus and shoot around the corner of the fountain. Leave one clip for the SWATs. The chopper will pass. After that, run to the wall again. Once again, SWATs will pop in and then you will have to repeat the process.
With a fast gun such as a MP5, sidestep and go left and right with your hand on the trigger at all times until it flies up. Do this on all sides until it gets destroyed. It usually requires two sides to take it down.
Activate the the "Unlimited health", "Unlimited ammunition", and "Unlimited Focus" codes. After shooting the tire off of the plane, An Agent will appear and turn into a SWAT member. The Agent will fly up with a helicopter. Tun as far as you can away from the helicopter and hide behind a pillar. Focus run and shoot with you best gun then run back behind another pillar. If the helicopter comes around the corner, then run behind a pillar that it cannot shoot you with. When you shoot the helicopter, it should lose life fast. Keep repeating this.
Listen for the sounds of gunfire and breaking glass until it stops, then get your MP5 and move to the right where the helicopter is located. Shoot it until it gets to the last window. Then, get a stun grenade and toss it immediately after the helicopter passes the last window to kill the SWAT team. Keep doing this until the helicopter crashes and explodes.