United and Delta Air Lines are alerting travelers of acceptable carry-on sizes at security checkpoints

(CNN) -- 'Tis the season when travelers loaded with holiday packages and luggage pile onto planes. And as the holiday carry-on crunch looms, flight attendants are again asking the federal government's help with the issue.

The American Association of Flight Attendants wants the Federal Aviation Administration to adopt uniform regulations governing carry-on baggage for all U.S. airlines, so that flight attendants have the rule of law behind them.

At present, each airline has its own rules on carry-on baggage. Some airlines set no size limits, while others require carry-on bags to be no larger than 10 by 16 inches (25 by 41 centimeters). Some airlines allow two carry-on pieces, plus a briefcase or purse, but others allow flyers to bring on only one bag, briefcase included.

Some airlines had been more lenient about carry-on baggage until they became a problem, said Ed Perkins, a spokesman for the American Society of Travel Agents.

"The overhead bins would be totally filled and people would be milling around in the aisles looking for space, and the net result was delayed flights," Perkins said. "So, the airlines said, 'We've got to do something about this, we're going to crack down and enforce our rules.'"

Flight attendants object to the disparity in rules enforced by the airlines, so their union is holding a news conference Wednesday to demand that the FAA require uniform regulations.

"We're not going to count how much luggage that you're bringing on, but we're going to say to you that if all of the luggage that you have will cumulatively fit in this sizer box, then you can bring it on," said Patricia Friend, a spokeswoman for the Association of Flight Attendants.

The flight attendants say limits are needed to cut down on injuries, improve safety, eliminate confusion and reduce delays.

United Airlines supports their proposal. Both United and Delta Air Lines are limiting carry-on size by installing templates over the openings of X-ray machines at security checkpoints.

"We firmly believe that the best policy is one that solves the problem the farthest away from the gate and boarding process," said Skip Barnette, vice president, Atlanta Worldport, Delta Air Lines.

However, Continental Airlines, whose passengers share some of the same checkpoints with Delta passengers, is challenging that.

"While it's perfectly OK for Delta to restrict its customers, it's not OK to impose that same restriction on Continental's passengers," said Sarah Anthony, a Continental spokeswoman. "What we have done is we have invested some $14 million to retrofit our airplanes to make our overhead bins larger."

One of the keys to reducing carry-ons is to improve baggage handling. A luggage manufacturers association recently conducted an Internet survey that revealed more passengers would check their bags if not for fears of them getting lost or damaged.

"A full 83 percent of the passengers traveling by air would indeed check their bags if they felt more confident about airline baggage handling systems," said Anne DeCicco, president of the Luggage and Leather Goods Manufacturers of America.

Passengers may have to consider other alternatives, like shipping their packages instead of bringing them along on the plane.

Based on a report from CNN's Business and Travel and Beyond. The segment appears weekdays on Early Edition at 7 AM (ET) and on Morning News at 10 AM (ET).