Your replies are very helpful. BTW, I didn't mean to say that an equipment change should qualify me for a downgrade kit. I meant only if the equipment change downgraded the *class of service.* Sorry if my own wording caused any problems.

Getting back to the topic, wouldn't there be less upgrade inventory (I class) on a 777 than a 747? Does this matter in terms of a confirmed upgrade being maintained? I only ask because 777s have 49 Business Seats, whereas 747s have 73 Business Seats.

Also, has anyone ever been downgraded to Economy because of this? Did you receive any compensation?

Speaking for myself, SIN-HKG is a very short flight (like SFO-ORD), but I'd realy hate to be downgraded to Economy for SFO-NRT, NRT-SIN or HKG-SFO.

FYI I got the very last I-class seat for the NRT-SIN segment. I paid $200 more for H class than the lowest Economy fare available, and booked this flight in early November (departing mid-March). I confirmed the upgrade at the time of reservation (meaning I wouldn't have bought the H-class fare if it would mean wait-listing).