|This is one of the setup missions for the FIB Heist, which is called Blitz Play. Prior to starting the setup missions, you should get a text from Steve Haines that says for all three of the protagonists to meet them at the usual spot. This places a "B" marker on the map, which initiates a cutscene with the same name as the heist.|
One of the setup missions for Blitz Play requires you to steal a Towtruck. When you get to one of the mission markers (Los Santos International Airport area), you will see an NPC working on a car. You can sneak up behind him and knock him out, but you don't have to. All you need to do is steal the Towtruck and bring it back to the lot where you met with the FIB to finish the mission.