You unlock the Agency SUV at Driving skill level 4. There are two relatively easy ways to get this achievement.
Have a friend go get a helicopter from the Agency Tower and have them bring it to you. Just drive the Agency SUV into the helicopter and it will unlock.
Find a Ramp truck and set it up near a tactical location. Have the SUV ready a little big away and call in a vehicle of some sorts. As the helicopter comes down. Drive up the ramp and hit the helicopter.
You dont need to co-op this one. I did it on my own pretty easily. -Just go to a Tactical Location. -Order a Ramp Truck -(If you dont already have one around) Order an Agency SUV -Line up the Ramp truck right in front of the TL DZ -Get in the SUV -Order in another vehicle (Any one works, but it has to be a vehicle) while in the SUV -Back up, and when the chopper comes down, launch off the Ramp truck into it