Severe weather moving across the eastern half of the United States on Tuesday appeared likely to disrupt the busiest travel period of the year, with more than 55 million people expected to travel by bus, train or plane before the Thanksgiving holiday.

Thunderstorms were forecast from the lower Mississippi Valley to the mid-Atlantic region between Tuesday night and Wednesday morning, while snow was expected to fall on parts of New England, according to the U.S. National Weather Service.

The severe weather was likely to cause delays and additional congestion during what the AAA group expects to be the busiest travel period in the country since 2019, before the COVID-19 pandemic struck.

Most of those traveling were expected to drive, AAA said, possibly motivated by a drop in gasoline prices from 2022. Around 49 million people were expected to get behind the wheel between Nov. 22 and Nov. 26, up 1.7% from the corresponding period in 2022, AAA said.

The number of Americans traveling around the holidays has rebounded in full force since the pandemic stymied the travel industry in 2020, AAA's tracking shows.

The Federal Aviation Administration on Tuesday said the bad weather would likely cause delays at some airports. As of Tuesday morning, the flight tracking website Flightaware showed that only nine U.S. flights had been canceled and 850 delayed out of more than 48,000 estimated scheduled flights.

Industry group Airlines for America forecast that U.S. airlines would carry some 29.9 million passengers between Nov. 17 and Nov. 27. That would be an all-time high, up 9% over the 27.5 million in the same period last year and up 1.7 million passengers over pre-COVID record levels.

"We have never seen that many people fly over Thanksgiving before, so I encourage everyone who's going to be traveling to pack your patience," spokesperson Rebecca Spicer said in a video address on the group's website.

(Reporting by Gabriella Borter and David Shepardson; Editing by Mark Porter)