WASHINGTON — The Thanksgiving air travel season is shaping up to be one of the roughest in memory as a surge in passengers is expected to swarm airports and carriers, which already are struggling to handle stiffened security rules, more checked luggage and a rising number of flight delays.

Travel consultants warn of added inconveniences resulting from thousands more people than last year passing through the airports. Novice fliers could gum up security checkpoints because they don't understand restrictions on gels and liquids. Airlines, which are already mishandling a record number of bags, may have further problems getting bags to the right destinations.

Bad weather also could disrupt holiday plans for travelers stuck on planes packed to near capacity.

Travel experts recommend that travelers get to the airport early, perhaps even three hours before departure at peak times. Passengers should also "hope for good weather," said Clay Foushee, an aviation consultant.

A combination of factors is to blame for this year's problems, experts said.

In August, the Transportation Security Administration banned most gels and liquids from the passenger cabins of aircraft after British police said they foiled a plot to blow up airliners with liquid explosives. A month later, authorities eased the ban, allowing passengers to carry small amounts of toiletries in a clear plastic bag.

The TSA recently launched a publicity campaign to educate fliers about the rules. Travelers are allowed to carry on gel and liquid toiletries as long as they are in containers of 3 ounces or less. Those containers must all fit into a 1-quart plastic bag with a zip top, officials said. Authorities and airport officials urged travelers to check airline and airport Web sites and the TSA site (www.tsa.gov) to learn more about the rules.

Starting this weekend, the TSA is increasing staffing and will open all airport checkpoints earlier to handle the increased traffic and ensure that lines don't get out of hand, said Kip Hawley, the agency's top official.

The TSA's bans have resulted in more checked bags that airlines are struggling to handle.

In September, the last month for which data are available from the U.S. Bureau of Transportation Statistics, airlines mishandled 8.25 bags per 1,000 people. It was the eighth-worst month for baggage handling since the government began tracking it, in 1987. It was even worse than the rate of mishandled bags recorded a month earlier, when the TSA quickly enacted its first ban.

Analysts expect the percentage of checked bags to increase in coming days because leisure travelers tend to check more luggage than business fliers do.

Some analysts urged passengers to bring an extra set of clothes in their carry-ons and consider not checking luggage at all to avoid any chance of lost bags.

"It will be a much smoother experience if you can carry on your bags," said Anne Banas, editor of SmarterTravel.com.

Airline executives said they will be able to handle any increase in checked bags. They also urged passengers to check in early and print out boarding passes at home to speed the process.

Once at the airport, expect big crowds. The Air Transport Association, a trade group that represents U.S. airlines, predicts that there will be 3 percent more passengers during the 12-day period starting today than there were in the comparable period last year. During peak dates — the day before Thanksgiving and the following Sunday and Monday — the trade group expects 15 percent to 20 percent more fliers than the average day this year.

Washington Dulles International Airport is expecting nearly 10 percent more travelers, or about 4,000 people daily, on average during the 12-day holiday travel period, than it would in September.

Experts urged passengers to avoid bringing wrapped gifts in their carry-on bags.

Once on board, passengers may feel more cramped than during the relatively slow fall travel season. Aircraft will be more than 80 percent full on average during the Thanksgiving travel period and much more packed on the peak days, according to the Air Transport Association.

Aircraft were about 75 percent full in September, for example, the group said.

Lisa Davis, editor of Frequent Flyer magazine, urged passengers to book rental cars and hotel rooms near airports so they have backup plans if their flights are scratched. Before booking a car or hotel, passengers should make sure the reservations can be canceled without penalty if they make their flights, she said.