REWARDS - $20,000, Jetpack is permanently yours, Airstrip becomes asset
Fly the jetpack to the green blip on the radar. As you approach the train, the guards will start firing on you. Target and kill each one as you move towards the front of the train. When you get to a box that might contain the "stuff," shoot it to open it. The first two boxes are empty, with the third one containing what you need. Once you open the third box, collect the green goo and head back to The Truth, designated by the yellow blip on your radar. Walk into the red marker at the airport to finish the mission.