I do not believe claims of airline profitability; I just remember what Warren Buffett said about the entire airline industry -- it's lost money over its entire history. If there are "profits" this year, they are riding off of capital investments made before the last bankruptcy, and aren't paying for capital replacement or maintenance.
They're going to be completely slammed into the wall by any increase in fuel costs, and their fleet is aging.
Your point about airline fuel costs is correct.
But the airline industry has become profitable in part because of massive consolidation and cutting of routes. There are now (with the American-US Airways merger) only three legacy carriers, plus one low cost carrier large enough to matter (Southwest). Plus, airlines have used regional partners and commuter airlines to fly smaller planes on many routes. This means less competition on fares, and more crowded planes-- load factors are way over 80 percent, which wasn't true at all in the past. Most flights are full. Plus, they have cut the dickens out of their labor costs, and renegotiated union contracts in bankruptcy.
The industry is reaping the benefits of all this, and almost everyone is making a profit. And if you correlate when food service declined and when it came back up, it correlates almost precisely with when the industry suffered record losses and when it made record profits.
I think too many people on train discussion boards want to view Amtrak as if is divorced from its subsidies-- like it's just another transportation provider which should, of course, offer great service to attract people onto the trains whose ticket revenue will then benefit the company and allow it to flourish. That's not Amtrak's business model, and none of us want it to be, really-- if Amtrak had to charge travelers fares that would allow it to actually turn a marginal profit on each seat sold, fares would be much more expensive. But that IS the airlines' business model, even if they historically haven't had a lot of success with it. Outside of outlier programs like Essential Air Service, airlines aren't receiving direct operational subsidies from the government. They need to make a profit, or at least break even, long term, or they go out of business. Amtrak can remain in business while losing money indefinitely, so long as the public subsidy is not pulled.
Because Amtrak's business model is closer to that of a public bus system-- get their farebox recovery ratio as high as they can and then make up the rest through government subsidies-- it can't view food service as a way to differentiate itself from competitors and entice more travelers onto the train. Enticing more travelers onto the train doesn't necessarily make Amtrak money the way it makes an airline money, because Amtrak isn't necessarily making a profit when it sells a train ticket to a traveler. Obviously, Amtrak needs to provide decent customer service, but the main goal is to deliver as much rail transportation as its subsidies and farebox recovery will allow it to deliver.
