Reply to Hawk:
We attempted to obtain clearance right up to the FIR boundary. The initial turn, to take up the hold, was at crew initiative.Informed CIS controller of action, advised awaiting onward clearance. Turning back inbound in the hold, CIS controller advised that he could not accept us holding due traffic, told us to return to previous CIS waypoint, no level change given. The airway was very busy eastbound and we were aware that following traffic at our level was now extremely close, requested immediate descent.This was given to the westbound quadrantal, not 500ft.Traffic seen on TCAS but passed well clear. Lost comms with Mongolian controller at 40nm.
How did we get out of the situation? When we passed our clearance number to the Mongolian controller, he read back the clearance number he was expecting. I wrote it down but it was not the same as ours. As we headed back into the CIS , a quick look at the company file of seasonal overflight clearances revealed that the clearance number he was expecting was the previous days flight, under a different flight number. Informed CIS controller we were changing callsign and requested return to FIR boundary. Passed the 'expected' clearance number and were allowed entry. A bit of bluff which you may see as a stroke of genius or totally unprofessional - up to you. The next problem was who would the Chinese think we were when we reached their FIR. Luckily they accepted our new I/D with no questions asked, but I spent an uneasy 6 hours waiting for someone to catch on. Only the Japanese controllers queried our flight number, but accepted a reversion to original with no problems. I can recommend adrenalin as an antidote to in-flight fatigue, but I don't want that experience again. Only 3 months to go, so not likely. Incidentally, according to a recent Flight magazine survey of the World's airforces, Mongolia does not possess aircraft capable of intercepting a high altitude jet, though China does.