Customer service has been suffering since American Airlines began charging for checked bags and the rest of the legacy carriers jumped on the ancillary fee bandwagon. Now, airlines are abandoning their coach passengers when it comes to their frequent flier programs. Every improvement for business class and first class passengers is coming at the expense of coach passengers.

More legroom in the front of the plane translates directly to less legroom in the back of the plane. Higher baggage fees translate to less overhead bin space in the back of the plane. Higher baggage fees are now being combined with worse checked baggage statistics, which only exacerbates the carry-on baggage problems. Front-of-the-plane meal services have become more lush as back-of-the-plane meals and snacks have been eliminated.

As airline frequent flier programs shift from providing benefits based on miles flown to amount of money spent, both individuals and companies need to reassess the impact on these programs. Airlines have been making the gulf between worst and first larger and larger over the past half-decade; now the most important part of frequent flier mileage programs is not earning free flights, but earning relief from having to fly in coach.

“I’m loyal to Delta. Loyalty means free bags checked, free upgrades, and sometimes free changes of an itinerary. Loyalty means I stuck with Delta through the tough years, but now that they’re on their feet financially, they’re telling me, ‘oh, we really don’t care that much about you as a loyal flier anymore. All we care about is your money,’ ” Mr. Sommer [a technology consultant who flies lots of miles and earns high elite status] said.

When money is thrown into the equation and cheap flights are eliminated as currency for entering the world of the elite fliers, the world of frequent fliers changes. So far, both United and Delta have dipped their toes into the world of pay-more-and-you-get-more benefits. You can bet that American is watching closely.

If the airlines can keep their “capacity discipline” (i.e. their refusal to compete with each other) intact and keep planes flying at almost 90 percent capacity, they will be able to squeeze even the most frequent of fliers into spending more to avoid the service abyss that coach has become. But, even in a constrained system like our current oligopolistic system, competition can grow again when the big players in the airline system abandon the masses.

Once upon a time, Southwest Airlines was considered Spartan with only coach seating. Now, the other airlines have been eliminating coach amenities one-by-one. Southwest’s service is almost luxurious compared to what one is now getting from American, Delta and United in the back of the plane.

The biggest bargain at Southwest is “Bags Fly Free.” This translates to faster boarding processes and more room in the overhead storage bins. Southwest still has peanuts and a couple of snacks for coach passengers. Now, when legacy carriers have all but eliminated free pre-assigned coach seating, Southwest’s boarding process is making more sense. As legacy carriers are forcing more and more passengers into having to pay extra to guarantee that they aren’t stuck in a middle seat, it is making life more difficult not only for the regular coach passengers, but for families as well.

Mr. Mayo, also a frequent business traveler, said that he sometimes flies one of the big three network airlines like Delta, but prefers to take Southwest Airlines whenever he can. He talked about another annoyance that travelers who buy basic coach fares encounter routinely when booking a flight these days: the unavailability of seat assignments at the basic fare. Instead, airline booking sites typically offer customers an upsell to seats that are available — for a fee.

Airlines are walking a tightrope. As they scale back coach services and make membership in their elite frequent flier levels more and more expensive to attain, the major carriers are playing into the hands of low cost airlines. It appears that legacy carriers may be following a path to only flying high-paying customers and abandoning the masses of leisure travelers. That would be unsustainable from a business point of view.

Someday, balance will have to come back to this aviation marketing system. Airlines will have to start providing customer service even to the hoi polloi.

Even bottom-feeders like Spirit and Allegiant (who prey on the unsophisticated travelers who do not realize the dangers of flying with carriers operating bare-bones route systems and schedules) will be able to grow and provide more consistent service. Small changes, over time, in their business models will make them comparable to the legacy carriers.

Or, perhaps, I should say slashed service by the legacy carriers will make even ultra-low-cost-carriers seem not so Spartan.

The more the legacy carriers advertise their upscale products in magazines and on TV, the more legacy carriers parade the unfortunates, relegated to the rear of the plane, past first-class passengers being served champagne while the unfortunates shuffle to the rear of the plane to fight for overhead storage space, and the more legacy carriers eliminate customer service and squeeze coach passengers, the sooner flier backlash will come.

What are your thoughts? Will the dearth of customer service for coach passengers result in a backlash against legacy carrier mistreatment of their passengers? Will the changes in frequent flier mileage programs make them less valuable to the majority of passengers? Will the legacy carriers eventually kill their golden goose?