(CNN) -- Air travel competition is heating up, and we're not talking about corporate profits and losses here. As airlines reduce flights and use smaller planes, passengers sometimes are jostling for storage space for their carry-on items.
Holiday travelers particularly risk raising the ire of grizzled business fliers, who depend on strict adherence to a set of written and unwritten rules to get them on and off of planes efficiently.
"Business travelers do this every day," said Joe Brancatelli, whose Web site, joesentme.com, is a destination for frequent fliers. "They know the rules of the sizes they're allowed to carry. They know the size of the space available to them on the plane they're flying, and they're prepared to hit the rules. What bugs them is when someone else doesn't know the rules."
Online discussion boards are full of stories about travelers who don't know the right way to put a bag in the overhead bin or who just bring too much with them.
"The lady next to me had so much stuff it was insane. I boarded the flight after she did, and she occupied the storage space of the seat in front of not only her window seat, but my seat too!" Michael Wand, a frequent flier from Honolulu, Hawaii, wrote on flyertalk.com.
Leisure travelers aren't entirely to blame, another frequent flier noted.
"Business travelers never want to check a bag; they want to get off the plane and go," said Seth Miller, a systems integration consultant in New York who has flown 145,000 miles this year.
The airlines' gate attendants and flight crews aren't helping, he said.
"There's clearly a problem. The rules, as much as they exist, are rarely enforced," Miller said. "The only place where it's not a problem, in my experience, is in Europe, and that's because they actually enforce the rules. If your bag is too big, you don't get to bring it on the airplane."
On U.S. flights, he said, "it's only the passengers doing the policing; the airlines are doing none of it."
Flight attendants, who have a lot to do before takeoff, can only do so much to police carry-on placement, said United Airlines spokeswoman Robin Urbanski.
"If a flight attendant is walking the aisle, there's no way for her to know if an item under the seat in front of you belongs to you or the person next to you," she said.
Even though it's not in their job description, flight attendants sometimes are forced to step in, said Miller.
"When it goes bad, there are literally fights on airplanes over things like, "No, that's my space," he said. "... The flight attendants do have to play arbitrator in those situations, and do that on top of everything else."
Still, most of the time it's not that bad, said Randy Petersen, editor and publisher of Inside Flyer magazine and insideflyer.com.
"It's not much worse than it has been for some time out there," said Petersen, who has 12 million frequent-flier miles. "... You don't hear a big outcry from flight attendants about a problem on board."
Fears that passengers would try to dodge checked-bag fees by carrying more onboard have not been realized in a big way, Petersen said. The airlines reported collecting almost $670 million in baggage fees in the second quarter of 2009, according to U.S. Bureau of Transportation Statistics. That indicates passengers generally accept the fees, he said.
Some leisure travelers who don't fly often simply are clueless about carry-on rules and etiquette, leading to bottlenecks as excess bags are gate-checked, Petersen said.
"There's probably more congestion in the air ramps than anywhere else," he said.
And that's where things could get dicey this holiday season, when millions of less-experienced travelers will be in the mix while frequent fliers try to go about their business.
"I don't see this as much of an issue right now. It might become more of an issue come the holidays," said Brancatelli. "... There are potential problems because we don't know how many people will be traveling."
Virgin America is experimenting with allowing passengers with no carry-on bags to board first. Those passengers can quickly take their seats rather than wait in the aisle while others stow their gear in the overhead compartments.
"We have not officially adopted this as a standard practice, but we've begun to explore it selectively," Virgin America spokeswoman Abby Lunardini said. "We will wait to get feedback from our teams to determine how long testing will occur and next steps, if any."
Passengers seem to like it so far, she said, but Brancatelli said boarding schemes -- window seats first, back to front, zones -- all seem to work equally poorly. Oddly, "cattle call" boarding seems to be the most efficient, he said.
Some airlines might limit passengers to a single carry-on item during the holidays, he warned. For efficiency's sake, carriers would do well to police the airport security queues and send would-be violators back to the ticket counter to check excess bags, he said. "The entire nation is on the move on Thanksgiving Day," Brancatelli said. "... Things are not bad right now, but Thanksgiving could be chaos."