Complete all levels of Heli Assault

In Heli Assault, you need to pilot a helicopter and escort one of your gangmates on land. Especially on the later levels, you'll find it virtually impossible to fly the chopper and work the guns at the same time, so you should definitely find a friend and do these missions in co-op. Enemy cars and eventually helicopters will tail both you and the car. The chain gun is worthless when compared to the rocket launcher, so use only that and try to make sure your car is out of the blast radius.

Every once in a while, your car will run out of gas, and you must go down and pick your teammates up. Go VERY slowly and carefully, or your teammates will fall out of the chopper. They won't die, but you may have trouble getting them back on. You'll no longer be tailed when you have them on your rudder, so just take your time and work your way to the objective.

There are two Heli Assault activities with 6 levels apiece. I recommend doing this in co-op so you can work towards the "Confidence Men" achievement as well as "Crime Lord".

This achievement rewards 15G after completion.