Many travelers may not realize it, but a seat ticket does not automatically entitle them to overhead space. Once space runs out, passengers must check their luggage at the gate, without paying a fee — and then wait for it at the baggage claim at their destination. Airlines are capitalizing on the fact that many fliers are willing to pay for carry-on convenience.
When Mr. Jacobs is not flying Delta, he relies on credit cards to jump to the front of the boarding line. "Those cards are worth it," he said. "I actually carry three different airline affinity credit cards."
He has good reason to get to the front. "As a chocolate salesperson, I need to bring my bags on the plane so the chocolate won't melt," he said. "When you're flying to a major customer and you pick up your bags at baggage claim and your samples are melted, that becomes a pretty big problem."
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As Mr. Jacobs has learned, there is only so much room.
And there is little chance that the free-for-all at check-in will ease soon. Airlines rely increasingly on fees, experts say. In 2012, domestic carriers collectively earned roughly $3.5 billion in checked-bag fees, up from less than half a billion dollars five years earlier, according to the Department of Transportation. Although exact figures are not yet available for early boarding revenue, analysts say it is increasing.
"There is growth there," said Jay Sorenson, president of the airline consulting firm IdeaWorksCompany. "Airlines will implement more of these fees."
Brian Easley, a career flight attendant, has watched the competition for overhead space become increasingly acrimonious.
"When someone gets to their row and looks up and sees something's there, they kind of freak out about it," he said. "They will throw a fit and they will start screaming at whoever put their stuff in their spot. We've had to throw people off the plane just because they refused to walk up a few feet and stick it in another overhead bin."
People will carry on anything and everything, Mr. Easley said. On one flight to the Dominican Republic, a passenger brought a kitchen sink wrapped in a trash bag. "Luckily, at the time we were flying this particular Airbus that just has a ton of overhead bin space."
Another time on the same route, a passenger carried on a car muffler. "I think in that case we did put it in a closet, next to a hula hoop someone had brought," he said.
Robert W. Mann, an airline industry consultant, said that although new planes were designed to accommodate more carry-on bags, "there's an infinite demand for overhead bin space," especially as airlines squeeze more people than ever onto planes.
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Airlines say they are providing an option travelers want.
"It's something our customers desire," said an American Airlines spokesman, Matt Miller. Charlie Hobart, a United Airlines spokesman, said, "We're always looking for ways to make travel more convenient for our customers." United let customers pay for priority boarding before its merger with Continental and reintroduced it this year. "Customers did enjoy it when we had it" before the merger, Mr. Hobart said.
Ed Bertsch is well versed in the fight for space. "Every plane is full and every full plane goes out with every overhead bin full," said Mr. Bertsch, who travels a few times a month for his job at a computer security consulting company. "I've been going to Texas, and sometimes there will be guys that put cowboy hats in the storage area. It's not a very considerate use of that space."
Not all planes are created equal when it comes to overhead space. Industry observers say the 50-seat regional jets are notoriously stingy with overhead bin space, and older models whose designs predated the ubiquity of rolling carry-on bags also are less accommodating.
In those planes, or on any crowded jet, the scramble for space can lead to bad behavior.
On one flight, Carl Hartman, a marketing executive in New York City, said another passenger pulled his carry-on out of the overhead bin, then reacted with hostility when confronted. "I said, 'No, find your own space.' They were angry and sort of shoved my bag back," he said. "No common courtesy."
"The other thing I've seen a lot of is trying to sneak other bags on," Mr. Hartman said. "There seems to be some unwritten rule that as long as you can shove everything into one bag, it counts as one."
Even debating these unspoken rules can lead to rancor.
Arthur Dunnam, an interior designer, travels frequently to meet with clients and often carries bulky product samples in a pair of bags. "Technically, it's two bags, but one's inside the other and it's still smaller than a roller bag," he said. But when boarding one flight about a year and a half ago, Mr. Dunnam got into an epithet-laden exchange with another passenger — "a busybody," he said — who objected to his bag-within-a-bag strategy.
Mr. Dunnam was kicked off the plane and had to take the next flight. "I will never let somebody get the better of me like that again," he said.