Watch a short video walkthrough of this mission.
Prerequisites
'A Drop In The Ocean' (Donald Love)
Brief
The packages that Claude picked up were a decoy. But Donald Love has discovered that his real objective was in the plane all along. So you are to go to the airport and get the package.
WARNING: Make sure that you complete 'Two-Faced Tanner' (Asuka) before accepting this mission. Otherwise the incomplete missions will become inaccessible to you and obtaining 100% completion of the game becomes impossible.
Walkthrough
Firstly, you'll need (at least) a sniper rifle and an uzi to complete this mission. Armour might also be useful. Drive to the airport in Shoreside Vale and get to the airfield, via the short road by the side of the airport building. Drive in front of the customs hangar until it says the "Columbian Cartel is here!" Then, drive a short distance back from the hangar, get out of your car and snipe them (there should be 4; 2 on the left, 2 on the right). Be careful not to blow the plane up; if that happens, you fail.
After you've shot all the Columbians, go inside the hangar and enter the airplane. It will tell you that the package is gone. Get out of the plane and go up to the Panlantic van. There will be a very short cut-scene, after which you'll need to drive to the construction site in Fort Staunton.
When you get to the construction site, you'll need to get into the lift in the middle of the blue building frame. There are several Columbians waiting inside the frame, so go to the top floor of the building on your left and snipe as many as you can. Then, go into the frame and shoot the remaining Columbians with your uzi. There should be a message telling you to take the lift up the tower once you've killed all the Columbians. Do so and watch the cut-scene that follows.
Finally, just get the package safely back to Donald Love and you will have completed this mission.
Reward
$50000, plus opening of second Asuka mission arc.
New Missions Available
'Escort Service' (Donald Love)
'Bait' (Asuka)