Matthew Van Dorne hadn't heard about Allegiant Air's new fee for carry-on luggage as he waited Tuesday to board a flight to Allentown, Pa., from St. Petersburg.It didn't take him long to think of a way to save a few bucks. "I'll just pack up some clothes and send them FedEx," he said.Las Vegas-based Allegiant Air, the dominant airline at St. Petersburg-Clearwater International Airport, will begin charging up to $35 each way for carry-on luggage today. Passengers are allowed to bring one personal item — a purse, briefcase or laptop bag that can fit under a seat — but will have to pay to bring anything larger.Booking and paying for tickets online can save passengers up to about $20 off the new fee.Allegiant president Andrew Levy told employees in an email that the changes are part of "an ongoing effort to develop an innovative, new approach to travel."At the St. Petersburg airport, the reaction to the new fee was mixed.Alice Shafer, a snowbird from Indiana who brings her luggage only as carry-on, will look for other airlines to meet her travel needs. Shafer lives on a fixed income and until now had flown with Allegiant two or three times a year."This extra fee is really going to put an extra burden on some of us," she said. "I was sorry to hear about it."She wasn't the only one upset."I think that's absurd," said Sandy Eichenberg, as she waited to board her flight to Allentown, Pa. "For carry-on? No."Allegiant Air is a low-fare carrier that makes about 70 flights a week out of St. Petersburg to 23 destinations, accounting for 93 percent of the airport's travelers. St. Petersburg-Clearwater International Airport spokeswoman Michele Routh did not want to comment on Allegiant's business decision or how it might affect the airport.Allegiant began charging extra fees — for food and drinks, even making reservations on its website — years before major airlines embraced the idea. The strategy helped Allegiant post 36 consecutive profitable quarters as of Dec. 31, a remarkable string given the ups and downs of the airline industry. It reported $194 million in revenues for the last quarter of 2011 and nearly $11 million in net income.Most airlines already charge for checked bags, with Allegiant's fee ranging between $20 and $35 depending on the route. In fact, U.S. airlines raked in about $2.6 billion in baggage fees alone last year, which helped many airlines post a profit.Allegiant, however, becomes just the second U.S.-based airline to charge a carry-on luggage fee. Spirit Airlines started charging customers up to $45 per carry-on bag in 2010.Arielle Coyne said the new fee in principle is "ridiculous," but because Allegiant's prices are so low, she doesn't really mind. Coyne, who flies from St. Petersburg to Knoxville, Tenn., every few months, normally carries a large duffel bag with her. The new fee will force her to look for a smaller bag that fits the free carry-on criteria."Allegiant is so cheap, it's not a huge problem," she said.John Josetti made the same point while he was waiting to board his flight to Chattanooga."(Allegiant prices) are just so far under everybody else," he said. "I don't think too many people are going to mind."Certainly not Lisa Allred, who is in favor of the new fee. She flies with Allegiant every year when she visits family in North Carolina.People always bring too many carry-on bags with them on the flights, she said, which adds time to boarding and unloading the plane. Rather than pay to check their luggage, they try to save some money by bringing it all on board with them. And when the storage compartments are full, the airline offers to check luggage for free to the last people to board the plane. She says that's not fair to people like her who paid to check their luggage."I'm glad they're (charging the fee) because that's very aggravating to me," Allred said.