Booked myself into 6B on a 777-200 three class SIN HKG, did this about 3 months ago for travel in Sept. Then a few weeks ago, I was moved to 6C, no big deal as it is still and aisle. But I notice now on the UA seat map that 6A is no longer shown, the seat is gone, blank and 6B has been given to someone else I presume, again no big deal for me. Seat Guru still shows a seat 6A on their seat map. What happened to the seat? I could understand it if 6B were gone, as I would figure it might be crew rest. Or maybe 6B is the crew rest and 6A is blanked out so no one can sit next to the crew rest.