Travelers who waited to make Thanksgiving trips are hitting the biggest crowds so far [Video]

Travelers who waited until the last day to make their Thanksgiving holiday treks need to be prepared for busy highways and the most crowded day yet this week at the nation’s airports.The Transportation Security Administration expected to screen 2.9 million people on Wednesday and more than 3 million Sunday, when many holiday revelers plan to return home.Air travelers had reason to give thanks — fewer than 50 U.S. flights had been canceled by midafternoon on the East Coast, according to FlightAware.However, more than 2,000 flights were running late, reflecting the tendency toward tardiness that is becoming normal at U.S. airlines. They were averaging more than 4,500 late flights per day since last weekend, and Wednesday’s count was likely to approach or surpass that number by nightfall.Wednesday afternoon was expected to be the worst time to travel by car, according to forecasters. Drivers headed out of town will be mixing with …