Favorable weather is helping get the Thanksgiving air-travel rush off to a relatively smooth start, but that could change in the next day or two.

By Tuesday afternoon, fewer than 100 flights had been canceled around the U.S. — a low number — but nearly 1,800 flights were delayed, according to FlightAware.

The largest number of delays — about 240 — was at Seattle-Tacoma International Airport, where dense fog was slowing the pace of departures and arrivals. Flights going to Boston and Newark, N.J., on Tuesday were also likely to be delayed, according to the Federal Aviation Administration.

Driving was challenging in parts of New England. The remnants of a recent snowstorm left messy road conditions across much of the region, and the forecast called for more snow on Wednesday followed by blustery winds and high temperatures in the teens on Thanksgiving Day in northern New England.

Rain, with snow in the higher elevations, could slow traffic Wednesday in much of California, Oregon and Washington.

The AAA auto club predicts that 54.3 million Americans will travel at least 50 miles from home between Wednesday and Sunday, the highest number since 2005 and about a 5 percent increase over last year. AA says 48 million will drive and 4.7 million will fly.

Looking at a longer, 12-day period, the airline industry trade group Airlines for America predicts that a record 30.6 million people will fly on U.S. carriers, up from 29 million last year. That’s more than 2.5 million per day.

Travelers should prepare for long lines at airport checkpoints. The Transportation Security Administration expects to screen about 25 million people, an increase of 5 percent over last year.

The Sunday following Thanksgiving is expected to be one of TSA’s 10 busiest days ever.