Airlines are increasingly cracking down on what passengers can take on board, and it's not just so that they can monetize baggage - although the money is good.

A study by IdeaWorks and CarTrawler in 2022 showed an already growing trend in monetizing carry-on baggage.

"From global network airlines to low-cost carriers, baggage is the top à la carte performer," said Jay Sorensen, the report's author.

Many low-cost carriers began charging extra for additional carry-on items several years ago. The larger airlines resisted such measures for some time, but have now begun to adopt fees themselves.

Baggage Revenues Rise

According to the study, which was published a couple of years ago and compiled data from 2021 when the industry was still recovering from the COVID-19 pandemic, American Airlines Group (AAL  ) generated a record $7.42 per passenger in baggage revenue in 2021.

You can also get a punitive charge for carrying on more than your entitlement, so you must do your checking before arriving at the departure gate.

One carry-on item is generally free. But if you try it on with more than that, they're getting strict.

And they're also getting strict on size, too. As long as it stowed overhead or under the seat, size didn't tend to matter. But now both Delta Air Lines Inc. (DAL  ) and Southwest Airlines Company (LUV  ) insist that carry-on baggage should stow under the seat.

Delaying Flights

At Irish low-cost carrier Ryanair Holdings Plc (RYAAY  ), there's a charge for checking in baggage, but one carry-on item that fits under the seat is free. Any additional carry-on items must be checked in, or you'll be punitively charged for it.

Ryanair has said that its carry-on luggage policy is also due to the time it takes for passengers to stow their carry-on and sit down, which can delay flights.

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