For those who are having problems passing the mission "Up, Up and Away!": Use the following strat to successfully pass it without any crashes:
1. Start and progress the mission normally until you destroy the enemy gunships.
2. Get in the helicopter and fly high above the sea. Use the route shown in the attached picture (red line).
3. DON'T TOUCH the winch controls at all (by default NUM2 and NUM8)
4. Once you picked up the truck, fly it directly to the airstrip and finish the mission.
5. Remember not to touch the winch controls at all times.