Flight attendants in the United States have been found to be selling desirable route assignments to their colleagues — again.

A year ago, American Airlines began to investigate staff who were using their seniority to get the most sought-after routes and then selling them, for an average price of $200, to more junior colleagues. Now United Airlines has found evidence that their cabin crew are doing this too, and is threatening to fire those who do.

The system for assigning cabin crew to flights varies from airline to airline. Flight attendants bid on assignments in order of seniority. People who have worked at the airline for decades usually get first dibs. They tend to opt for the routes that pay the most, take them to the best destinations and include cushy hotel stays — or offer a combination of these factors. Long-haul flights tend to be more desirable, since many flight attendants get paid according to flight duration.

For instance, one attendant en route to the Bahamas desperately tries to avoid the 18-minute hop from Florida to the archipelago’s closest island because the pay is so low. The result is that some flight attendants given the desirable routes may decide to sell them to colleagues further down the pecking order, which is forbidden by company policy at many airlines.

Economists and airline executives would argue that this system is inefficient. Senior flight attendants are given something free that is clearly valuable, which exacerbates existing pay inequity between senior and junior employees. Some European airlines, including Ryanair, the continent’s cheapest, assign flights to employees without regard to seniority, but simply to meet demand.

The Ryanair solution is not popular among all cabin crew, whose job satisfaction partly rests on having some sort of control over the routes they fly. But the airline industry already has a solution that would ensure maximum efficiency and respect staff choices: dynamic pricing.

The price a passenger pays for a flight is based on demand for that route — if demand is higher than supply, the price of the ticket increases.

Why shouldn’t flight-attendant rotations work in the same way? Instead of paying the same hourly rate for each route, airlines could cut the pay for the most sought-after routes and raise it for the least desirable. Designed properly, staff should lose the incentive to abuse their seniority. That would be good news not only for cabin crew, but also for the fliers who benefit from happy flight attendants.