I can attest to that one. Got stuck in Moscow a few months ago when clueless Aeroflot agents couldn't make heads nor tails of our ZED passes until after our flight to Hanoi left. No Russian visas, so we'll just hang out in the airport till tomorrow night's flight, right? Wrong. Max of 24 hours in the airport without a visa. Not 26. They threatened to deport us back to Amsterdam! Aeroflot wouldn't accept our ZED pass for any routing but SVO-HAN, fortunately DL had seats open to JFK the next day. Never made it to Vietnam but at least I didn't get deported by the Ruskies!