cerealmarketer's "666" was in the ticket number, a relatively long series of digits largely ignored by travelers. How about the Northwest 747-400 with the callsign N666US? It doesn't bother me, in fact some fellow travelers and I refer to it jokingly as Air Satan and take extra joy in flying on it, but I can't help but wonder what would happen if some jittery infrequent travelers requested reaccomodation at the gate.

N666US arrived from Boeing in 1989 and held the honor of taking Northwest's last landing at Hong Kong's old Kai Tak airport. It's a 747-451 (s/n 23821).

Here's a link to some pics of N666US.