Add $5 each day you wait to buy Thanksgiving airfare

Harriet Baskas
Ian Waldie | Bloomberg | Getty Images

Thanksgiving is always the busiest and most lucrative time of year for airlines, said FareCompare co-founder Rick Seaney, and travelers will need to be nimble in order to find deals on airfares.

"The good news is that prices are up only about 1 percent over last year," said Seaney. "The bad news is that last year prices were the highest we tracked in eight years."

(Read more: Shutdown threatens holiday sales, NRF says)

For those who don't yet have tickets, don't dawdle, says Seaney.

From this point on, every day you wait to buy a ticket for holiday travel time will add another $5 to the price of your ticket, says Seaney, based on his company's analysis of holiday airfare trends.

That means waiting until October 31st could add upwards of $140 to your total airfare.

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And if you put things off and don't even start shopping for your Thanksgiving airline ticket until the beginning of November, "all bets are off," said Seaney.

The most expensive days to fly over the Thanksgiving holiday will be the Wednesday (Nov. 27) before and the Sunday (Dec. 1) and Monday (Dec. 2) after. The least expensive days to fly will be on Thanksgiving Day (Nov. 28), followed by the Monday and Tuesday before and the Saturday (Nov. 30) and Tuesday (Dec. 3) after.

(Related video: A 360-degree view of luxury travel)

You may not be able to get a really cheap ticket, but you can try to save some money by being willing to take a flight that requires one or more connections or by booking an overnight or red-eye flight. Mixing days so that you travel on a popular (expensive) day in one direction and a less popular day on the other can shave costs and traveling with a just a carry-on bag will, of course, allow you to avoid checked-bag fees.

"The bottom line is: don't wait," said Seaney. "There's more demand than supply and airlines have zero incentive to discount. If you do procrastinate, not only will you pay a hefty price, but you won't get the seats you're looking for."

—By Harriet Baskas, NBC News.