The ground to air defense mission
The ground to air defense mission is a new mission type available in ysflight as of the 2012 test version. At this time it is unknown whether or not player-controlled ground objects will be accessible on servers.
The mission currently consists of a player being given a deadly AAA truck controlled by mouse, rudder and throttle. The player must use this to fire at incoming enemy attack aircraft, who are intent on destroying your IFF's ground assets with their payload. These enemies spawn endlessly until a time limit is reached, similar to the endurance mode. The current ground defense truck is a Gepard. It has infinite ammo, and its targeting system seems to consist of two points that track the enemy aircraft distance-wise so that you might point the tracers, and thus destroy, the aircraft.