You now have 12 minutes to escape from The Compound and make your way to the airstrip where Riley is. You cannot use fast travel and there are a lot of enemies between you and the exit of the compound. Just run past them all, as you will also encounter Heavies. When you hit the gate, you will get a checkpoint.
Once you’re outside, grab the vehicle by itself and start driving towards the airstrip. It’s best to not stick to the road, but drive through the grass, as there will be enemies on the road, including some with RPGs. You will eventually have to cross Littlegate Bridge, which raises as you’re passing it. As long as your vehicle isn’t too damaged, it will make it over the bridge.
As you near the bridge close to the airstrip, a helicopter will come and harass you. You have one of two options to get rid of it, either with a RPG (if you happen to have one on you) or man the machine gun on the vehicle and shoot it until it explodes. With that down, head inside the airstrip and the timer will stop.
There are a lot of men inside the airstrip, so use cover and take your time in taking them out, since you don’t have to worry about the timer anymore. Go along the left side of the airstrip and eventually a building will have a yellow outline surrounding it, which is where Riley is being held. If you have any C4 or other explosives, take out the Heavy behind the fence if you can, then go up to the door and rescue Riley.
It’s now time to escape and as you go towards the exit of the building, more men will show up, including a Heavy with a Flamethrower. Get near the chopper and it’s time for Riley to learn how to fly one. While he’s doing that, you will man the machine gun and have to protect the helicopter from the enemies. As he’s flying around, you will have to shoot a bunch of enemies on foot, some with RPGs, enemies in trucks, enemies in boats and even some helicopters. When all the enemies are dead, the mission will end.