Holiday travelers stressing over crowded flights, shrinking leg room and snaking security lines can add one more: There’s a greater chance this Thanksgiving week that their bags won’t arrive at their destination.

An estimated 4.8 million passengers are expected to fly between Wednesday and Sunday, according to AAA, making this Thanksgiving the busiest U.S. airports have seen. About 165,000 of those passengers are expected to go through Lambert Field.

More travelers mean more bags, and more bags mean more passengers left empty-handed at the carousels.

The rate of lost luggage has moved upward for three years. But in September, the month after stricter carry-on security rules led to more checked luggage, the rate of lost bags shot up 81 percent from the same month last year, numbers from the Department of Transportation’s Bureau of Transportation Statistics say.

There were 8.25 complaints per 1,000 passengers in September, the highest rate since December 1988. About 383,000 bags were reported as lost, or "mishandled," as the federal government labels it.

Doris Broadus, of Columbia, Mo., wanted to avoid the possibility of her luggage getting lost, as well as security hassles. So she shipped her essentials by mail to Dallas earlier this month, days before flying to see her daughter and grandson.

"It was easier that way," she said, after her return flight to Lambert.

The culprit, in part, is changing security rules. Rules concerning liquids, creams and gels in carry-on bags changed twice this summer. The items initially were banned, but now things such as hair spray, lotion and lip gloss are allowed in small quantities. The Transportation Security Administration is embarking on a "3-1-1" campaign to remind passengers how much can be carried onto a flight: Three-ounce containers, packaged in one clear quart-sized, resealable bag. One bag per passenger is allowed.

The number of checked bags has tapered off since the TSA relaxed its rules.

"There’s still a bit of an increase, but not overly," said Amy Lattimore, an assistant customer service manager for Southwest Airlines.

The mix-ups tend to happen minutes after travelers take their bags to TSA workers for screening. After sending the bags through the large scanning machines, screeners put them on a conveyor belt that runs through Lambert’s ceilings and floors into the bag room. A laser scans bag tags and directs luggage either to a baggage pier or a carousel, depending on the airline. Each pier holds bags bound for two flights. Ramp workers put them on carts by destination and load them onto the planes.

Some airlines send bags to a carousel that could have luggage for as many as five flights. It’s up to airline workers to get the right bags on the right carts. One mistake, and they’re off to the wrong places.

"The system isn’t foolproof," said Kevin Christ, of Airport Terminal Services, which handles baggage delivery and other ramp services for charter flights at Lambert. "What makes it confusing is when you’ve got several flights to the same place going out close together, and going out on the same pier."

Historically, December is the worst month for lost luggage, because of increased passenger loads and the amount of luggage travelers take with them.

Losing those bags is among the stress triggers that send up blood pressure, according to the results of a consumer report released last week by Amadeus, a technology provider to the travel industry. Even with the surge in numbers, still fewer than 1 percent of passengers arrive without their luggage. But 37 percent of passengers are concerned about it, the report says.

Most airlines require that bags be checked at least 30 minutes before departure or they’re marked "late" and have greater chance of not making the flight. Some airlines say that if a suitcase marked "late" is lost, it’s not eligible for delivery to the owner; it must be picked up at the airport.

It’s unclear how many of the roughly 383,000 bags reported lost in September were eventually returned to their owners.

Luggage Express Found, a company that delivers lost bags to passengers in most major metropolitan areas, has seen a 65 percent increase over the past year in the amount of luggage airlines returned to passengers, said Richard Altomare, chief executive of Universal Express, which owns the delivery service. The company has a luggage shipping service, which allows travelers to send their bags ahead of them. Its numbers are up 76 percent.

The number of air travelers who send their bags ahead of them is small but growing.

"I just got off the phone with Santa Claus, and he’s thinking about using our luggage service," Altomare said.

Thanksgiving travel predicted to go up

Airports and highways will be crowded this week as an estimated 38.3 million Americans travel for Thanksgiving, according to American Automobile Association estimates.

Of that:

31.7 million will drive, up 2.6 percent from last year.

4.8 million will fly, up 3.2 percent.

1.8 million will go by train, bus or ship, about the same as last year.

Those renting cars will find prices up about 21 percent. Airfares are up about 4 percent, and the average hotel cost up about 16 percent.

The auto club reports the average price for regular gasoline in St. Louis was $2.06 Monday, compared with $1.99 on the same day last year.

The equivalent prices for East St. Louis were $2.21 Monday, and $2.01 last year.

The national average Monday was $2.24, compared with $2.22 one year ago.