Steal an Airplane at McKenzie Airfield.
If you are either extremely skilled or extremely dumb, you do this without Player Saved Outfits and thus without any kind of armor.
If you have a Kuruma this will help a lot! You have to take out a lot of enemies at the airfield. They will come in waves. When you have cleared all except for 3-4 enemies, drive the Kuruma to the hangar and the pilot steps out. The Kuruma now have to clear the strip for cars as the Vagos will park there to prevent the plane to take off.
If some one, preferably with heavy armor can take the cars out with an RPG that is also fine.
When the plane has left, players in the Kuruma can continue to shoot the enemies – but they have to stay alive until the plane lands in LSIA. So stay in the Kuruma and LEAVE the air field.
There are two ways to do this.
1. If you are on the Cargo team without any armor, climb the containers next to the ship and take out the visible enemies with a sniper rifle. Then board the ship and be prepared to step aside between the containers on board to eat snacks and put on armor. This way takes a lot of time as you can’t snipe all of them.
2. Climb the crane at the front of the cargo ship. There is a parashute on the top of the crane. Take it and shoot the two guards you can see below you. The container is right behind them. Jump from the highest point as the shute will not open right away!
Take the car and drive at the railway almost all the way to the destination.