ATLANTA — U.S. airlines never met a fee they didn't like. Until now, it seems.

Five major carriers on Sunday agreed not to follow the lead of a small Florida airline that plans to charge for carry-on bags. Their commitment comes just in time to keep travelers from running for the exits during the peak summer flying season, but it is doubtful it marks a change in strategy.

Airlines are going to tack on every fee they feel they can get away with because it bolsters their revenue stream while allowing them to keep base fares lower. They just don't feel like passengers will tolerate losing their sacred free carry-ons — at least not right now.

The promise to New York Sen. Charles Schumer from American Airlines, Delta Air Lines, United Airlines, US Airways and JetBlue Airways comes despite the fact that some of those same airlines are expected to report first-quarter losses next week. They were stung by higher fuel prices and the heavy February snowstorms.

Ancillary fees for air travel — including baggage fees, reservation change fees and other miscellaneous operating revenue — have been piling up. For U.S. carriers they totaled $1.95 billion in the third quarter of 2009, roughly 36 percent higher than for the same period a year earlier, according to the most recent government data available.