MIAMI (CBS4) – If you plan to hit the road or catch a flight out-of-town for the Thanksgiving holiday, pack your patience.

More than 40 million Americans are expected to travel by plane or by automobile between Wednesday and Sunday, according to AAA.

Travelers at Miami International Airport Sunday night got a preview of what was to come for the remainder of the Thanksgiving week. Some security lines stretched well beyond the typical 15 minutes.

“It’s a little hectic,” said Frankie Melendez. “We missed our flight. We’re trying to get a second reconnecting flight. It’s crazy.”

An extra security line was opened after one got so long people started crowding the TSA attendant.

“Very slow,” John Molina said. “We’re going to be here for like 2 hours in this line.”

Surprisingly, many of the people traveling Sunday night were actually trying to beat the Thanksgiving rush. Most told CBS 4’s Lauren Pastrana they weren’t traveling for the holiday, but rather wrapping up a prior trip.

The number of holiday travelers at local airports is expected to peak Wednesday.

Nearly 900,000 passengers will pass through MIA, according to airport officials. Fort Lauderdale-Hollywood International Airport officials predicted more than 500,000 people will arrive or depart over the holiday period.

With so many travelers, a good seat will be hard to come by, unless you know the tricks of the trade.

“Sign on to the airline’s website exactly 24 hours before the flight takes off so you can get the best seat assignment,” suggested Bryan Glazer, President of JetPlane Public Relations. “You need to understand, you’re competing against a hundred different passengers trying to get the best seats on that flight.”

Glazer said you should have a friend or relative log online at the same time so they can try securing seats, too.

If you’re only planning a quick trip, Glazer said airports won’t be as crowded on Thanksgiving Day.

“If you’re traveling within the state of Florida on Thanksgiving week, it may actually be less expensive to fly than it is to drive, especially long distances.”

Glazer said Fort Lauderdale-based Silver Airways has one-way deals starting at $81 dollars before tax departing Thursday.

AAA predicts 39.1 million people will drive to their holiday destinations between Wednesday and Sunday, compared to 3.14 million people who will fly there.

Florida drivers can expect to pay on average $3.33 per gallon of regular unleaded gasoline during the holiday week.