(CNN) — The United States' busiest travel days of the year are likely to be even more complicated for travelers flying through U.S. airports.
Security will be tight in the wake of terrorist attacks in Paris and the suspected bombing of a Russian passenger plane, compounded by the highest number of Thanksgiving holiday travelers since 2007.
The Transportation Security Administration has "doubled down" on security at airports, and wait times have gone up, although not dramatically, Homeland Security Secretary Jeh Johnson said Sunday in New York.
The Russian Metrojet crash in Egypt on October 31 prompted security enhancements at airports overseas that have flights to the United States, Johnson said.
Despite the beefed-up security, "we know of no specific credible threat of a Paris-like attack directed against the U.S. homeland," he said.
An estimated 46.9 million people will travel 50 miles or more from home during the Thanksgiving holiday, an increase of 300,000 over last year and the most since 2007, according to AAA Travel.
The vast majority of those -- 42 million Americans -- will be driving.
Some 3.6 million Americans are flying to their holiday destinations, a 0.1% increase from last year.
AAA Travel defines the Thanksgiving holiday period this year as Wednesday, November 25, to Sunday, November 29.
Although the TSA won't reveal what additional security measures will be taken, former TSA head John Pistole said to expect more random hand swabbing for explosive residue, bomb-sniffing dogs, laptop checks and shoe removals, even if you have TSA Pre-Check.
"The key is to be unpredictable," Pistole said.
Decreased staffing levels of TSA airport personnel may contribute to longer wait times. There were 40,609 full-time airport screeners in October, 5,000 fewer than the 45,874 there were in October 2011.
Asked how the agency will get around the decreasing staffing levels, TSA officials declined to comment.
The busiest travel days of the Thanksgiving season are expected to be Sunday, November 29; Monday, November 30; and Wednesday, November 25, respectively, according to Airlines for America, an airline industry group. The lightest travel days will be Thanksgiving Day and the Friday after, the group estimates.
There's good news for the millions of travelers driving this Thanksgiving. Prices at the pump will be at their lowest since 2008, according to AAA.
The average price of gasoline nationwide is $2.08, 72 cents lower than last year's Thanksgiving Day average.
"Motorists are saving around $11 for a full tank of gas compared to this time last year," AAA spokesman Mark Jenkins said in a statement.
Though airports receive a lot of attention, driving is statistically far more dangerous than flying.
For any means of transportation, vigilance and preparation are key to safe holiday travel.
AAA recommends having vehicles inspected by a reliable repair shop before departure and urges motorists to check the condition of their batteries and tires before leaving home. It's especially important to prepare for driving in winter weather.
Fliers can expedite security by leaving liquids and perishables at home, including that famous pumpkin pie.
It's true that pies aren't strictly forbidden by the TSA in carry-on bags (cranberry sauce is subject to the 3-ounce rule), but it may require extra screening, slowing security lines.
And early Christmas presents should should not be wrapped, so security officers can easily inspect them.