Expect the airports to be packed this Thanksgiving: Some 26.4 million passengers will fly over the 12 days surrounding Thanksgiving, an increase of 1.5 percent from last year. That’s according to Airlines for America, a trade group that represents the industry.

The 12-day holiday travel period begins on Nov. 21 and ends Dec. 2, reports the group. The busiest day will be Nov. 30, the Sunday after Thanksgiving: 2.6 million passengers are expected to take to the skies on U.S. airlines. The lightest travel days will be Thanksgiving itself, Nov. 27, and Friday, Nov. 28.

"Demand thus far this year for air travel has been strong, and we expect that to continue through the Thanksgiving holiday period,'' said John Heimlich, Airlines for America vice president and chief economist, on a call to journalists.

The busiest airport will be Atlanta’s Hartsfield-Jackson International Airport, followed, in order, by Los Angeles International, Chicago O’Hare, Dallas/Fort Worth, New York’s JFK, Denver International, San Francisco, Phoenix Sky Harbor, Charlotte-Douglas and Houston George Bush International.

Meanwhile, the airline industry’s huge profitability, thanks in part to lower fuel prices, is set to be the highest since 1999. In the first nine months of 2014, the nine largest U.S. carriers reported net earnings of $6.8 billion, resulting in a profit margin of 5.7 percent. That’s up from $4.5 billion in 2013.

But don’t expect boosted profits to translate into lower fares. Travel booking site Orbitz says that Thanksgiving fares are up 2 percent from last year. Instead, said Heimlich, the airlines are reinvesting profits into their operations to handle consumer demand.

“Improving finances are enabling airlines to add seats to the marketplace and reinvest in the customer experience – in the cabin, at the airport and online – at a rate exceeding $1 billion per month,” said Heimlich.