Easy "Three Man Army" achievement

First, complete the "Mr. Philips" story mission to unlock Trevor as a playable character. Then, call the other two playable characters with your in-game cell phone. Pick them up with a four door car, and go to the Los Santos International Airport at the southern end of the map. Once you enter the airfield, you will immediately get a 3-star wanted level. Keep driving from one end of the airport to the other for three minutes while making sure not to lose the cops to get the "Three Man Army" achievement. To make this a little easier, upgrade your car with the bullet proof tires from the car repair shop. Note: It is possible to miss this achievement depending on the game ending you obtain. Thus, make sure to get it before the last five story missions.