This just happened to me in POD. I was about to take off in a MD-530 Scout off the roof of the small building under Russian control in the Southern Providence.
I suspect it had something to do with the fact that the winch was deployed before I entered, but anyway, my whole screen began flashing between regular fog and some shade of brown. According to my radar, I was completely surrounded by a restricted area, however a subtitle thing popped up shortly after saying i was still in East Pyongyang. I had turnd on the infinite health cheat a little before this happened, but my helicopter was somehow taken down to 66% health and turned invisible. Most interestingly, I was sent 2,147,483,648 meters underground, the distance of about 168 Earths. The game crashed shortly after this event, either by attempting to go lower than the system is prepared to compute or because I attempted to look as far up as possible.
Results have proven unreproduceable.