Instructions
Get into a UH-60 Blackhawk helicopter. The chopper is exclusive to the U.S. Army side and is typically located at the back of the force's main base.
Press and hold the "W" key to make the helicopter ascend into the air. Eventually, an enemy aircraft is more than likely going to lock onto you with a missile.
Right-click to deploy flares when the missile is just a couple helicopter lengths away from you. The flares will exit from the rear of your aircraft and will cause the missile to explode.