Good point, sbm12. There seems to be a new trend: Fist, Business, Economy --> Business, Economy Good (Economy Plus, Economy Comfort, etc), Economy Bad (Economy Discomfort, Economy Minus, Voyager, etc)

The cost of a F cabin is part of larger investments in staff training, dedicated lounges, ground service contractors, bonus miles credits and I suspect many more. Little wonder if most airlines cannot manage to make it work, besides very few top players, whose profitability I would not swear about.

If Int'l First is profitable enough for certain routes, then an airline will want a fleet that can always provide Int'l First for those routes, which means that they will have extra planes with the First Class cabin. On any given day, some of those planes will be flying routes where Int'l First is not profitable. I think that an airline like United might retain a certain number of three-class planes even if they cut back on Int'l First overall so they can continue to milk the routes where Int'l First pays and cut their losses on others.