American is no longer alone with its $15 fee to check your first bag on a flight. United and US Air just announced they, too, will charge a similar fee.

Furthermore, US Air will soon charge $2 for soft drinks and $7 for alcoholic drinks, about what you'd pay at a swanky nightclub.

The demise of the standard, all-inclusive airfare and the gathering momentum of a fee-driven model (pioneered by European carrier Ryanair) continues toward something approaching commoditization. Commodities are a terrible business for customer loyalty.

Airlines, of course, are in a horrible spot. The rising price of
oil, driven by futures traders that make Wall Street bankers look like
Mother Teresa, is flushing revenue models down the
toilet. Fees for bags and drinks are short-term sandbags against a flood of red ink. The sudden appearance of fees could threaten airline loyalty, which is big business.

Which raises this question: Is the future of airline loyalty programs in paid membership? Will airlines follow the Costco model?

Research in the 1990s by Alan S. Dick in the Journal of Product and Brand Management might indicate yes. In conducting computerized shopping experiments focused on video store rentals, Dick found that a membership fee can become "psychologically amortized" in the minds of customers, making them "hesitant to switch as the would feel uncomfortable 'wasting' the investment" of the membership fee.

In other words, membership fees increase repeat purchases.

A membership fee is a sunk cost, like that gym membership even though you only go twice a year. It's free money for the gym, and free money is something airlines need desperately.