Ok take a look at the screenshot and notice aircraft that have violated a nav zone. They just came off a tanker and for some reason instead of the RTB chose another tanker and plotted a course through a no navigation zone. The tankers are all on the same mission.
Up to you how you want to handle this. I think if they'll crash due to fuel it is probably ok, although easy to be a hoser and cheat abit using this too. Up to you.

"Smart people just shrug and admit they're dazed and confused. The only ones left with any confidence at all are the New Dumb". HST