Originally Posted by
zcat18
Hobo--not necessarily. If you're on a 2-class aircraft, and the higher level of service is only half-full, then yes, it would seem to be a valid statement(although I was always under the impression that certain bargain basement or sale fares were not eligible for upgrades, even if there is nobody in the premium cabin, but I could be wrong). If you're on a three-class aircraft, though, which describes most long-haul planes, then my understanding is that you need to "buy" two upgrades to get from coach to first (maybe three, if Economy to Economy+ is considered an upgrade, which I'm not sure about). Of course, you can ask the same question about business, but I believe that load factors tend to be higher in business than they are in F.
You generally cannot buy a double upgrade. You need to buy a C ticket and upgrade to F. But the OP asks, in general, about upgrading, which includes both Y to C, and C to F. For the general member who doesn't fly up front all that much, they are apt to see a bigger bang for their buck going from Y to C on a 3-cabin, then from Y to F on a 2-cabin.
And flying on a non-upgradeable fare has little to do with the configuration of the aircraft. You won't be able to upgrade regardless of load!