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If you’re traveling this holiday weekend, you already know you'll be hitting the crowds. But this year the roads and skies will be even busier than usual — and new rules at the airport could slow things down even more.

AAA is projecting that 50.9 million Americans will travel 50 miles or more away from home this Thanksgiving, a 3.3 percent increase over last year and the highest Thanksgiving travel volume since 2005.

“A strong economy and labor market are generating rising incomes and higher consumer confidence, fueling a strong year for the travel industry, which will continue into the holiday season,” said AAA's Bill Sutherland.

An estimated 28.5 million passengers are expected to travel on U.S. airlines during the 12-day Thanksgiving air-travel period, also up 3 percent over last year, according to the trade organization Airlines for America.

All those fliers mean more stress and longer lines at airports — and this year, new security checkpoint rules for many passengers might add to the congestion.

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All electronics must be screened

In an effort to strengthen screening procedures for carry-on items, in July the Transportation Security Administration began requiring travelers going through the standard (non-TSA Precheck) lanes to remove all electronics larger than a cell phone from their carry-on bags and put those items in the bins for x-ray screening.

In the past, it was mostly just laptops that needed to be removed from carry-on bags.

The new remove-all-electronics policy was tested at 10 airports during the summer and fall, but that rule is now being enforced at 180 airports nationwide, with more on the way. That means security checkpoint lines in many airport may slow down over the holiday as more passengers are asked to fish out the electronics in their carry-on bags and more congestion (and grousing) in the post-screening “recombobulation” areas as travelers spend extra time repacking their bags.

To help ease some of this congestion, over the busiest holiday travel days TSA will increase checkpoint staffing and put more bomb-sniffing dogs on duty. In many airports, some checkpoints will also be opening earlier than usual.

Another tool that might help move things along at security checkpoints this year is an increase in the number of automated screening lanes. The lanes have bins large enough for roll-aboard bags and allow multiple passengers to load their belongings simultaneously.

The TSA says there are now 86 automated screens at nine airports, including Atlanta (22), Los Angeles (10), Chicago O’Hare (5) Newark Liberty (17), New York JFK (19), LaGuardia (2), Minneapolis-St. Paul (4), Dallas-Fort Worth (4) and McCarran Las Vegas International Airport (3).

As always, “The best way to ensure a quick trip through the security screening process is to prepare, prepare, prepare,” advises the TSA.

Nearly 51 million people are expected to travel this Thanksgiving. NBC News

And leave your firearms at home.

Firearms are not permitted in carry-on bags at airports. Yet, despite a recent report on undercover tests that found TSA screeners fail to detect a high number of weapons, as of October 31, TSA had found 3,600 firearms in passengers’ carry-on bags. That number already exceeds the record-setting number of 3,391 firearms found in all of 2016.

That tally doesn’t include the 90 firearms (77 loaded) found in carry-on bags at airports during the first week of November, nor the loaded handgun found in the carry-on bag of a Southwest Airlines pilot getting ready to board a plane at St. Louis Lambert International Airport.