The Thanksgiving and Christmas holidays are among the most popular times for Americans to travel. For example, an estimated 41 million Americans took a trip last Thanksgiving, despite record prices for both gas and airfares.

New estimates are now out for airfares from the “fareologists” at Farecast, which is now part of Bing Travel. [full disclosure: Peter Greenberg is a contributor to Bing Travel]

So will better deals on travel be available this year, or are Americans in for a pricey holiday travel season?

Though airfares hit record highs last year, during the 2009 holiday travel season travelers should see significant relief on prices.

During the long Thanksgiving weekend, the nationwide average ticket price is predicted to be down by more than 20% compared to last year. As you might expect, the most popular Thanksgiving itinerary is a Wednesday departure and Sunday return.

If you can travel on Monday instead of Sunday, you’re likely to save an additional 10%. And as Peter always points out, traveling on Thanksgiving itself is not only less stressful, but cheaper, too.

More holiday travel articles:

• Travel Cheap With “Dead Week” Deals
• Italy for the Holidays? How Italians Celebrate Christmas
• Holiday Travel Gadgets for Geeks for Under $100
• Winter Holiday Food From Around the World

As for Christmas itineraries, the most popular one is also a Wednesday departure and Sunday return, but there aren’t as many opportunities for scoring cheaper flights by shifting your travels by a day or two. Instead, try flying on Christmas Day for savings of around 10%.

So now you know the ideal time to travel, but what about the best time to book your tickets?

While Peter recommends booking tickets on domestic flights about 45 days in advance as a general rule, the main exceptions are peak travel periods–especially the Thanksgiving and Christmas holidays.

For peak travel periods like these, it usually pays to start looking much earlier. For example, for Christmastime flights, Bing Travel notes that there are often price cuts in October, but they are erratic and don’t usually last long.

Bottom line: Starting looking for Thanksgiving flights now. As for the Christmas season, if you’re flexible with your schedule, you can probably grab a good fare in the first two weeks of October if you keep your eyes peeled. However, if your schedule is less flexible, it’s probably a good idea to nail down a decent fare now.

By Matthew Calcara for PeterGreenberg.com.

For more, check out Looking Into the Fare Future with Farecast.

More holiday travel articles:

• Travel Cheap With “Dead Week” Deals
• Italy for the Holidays? How Italians Celebrate Christmas
• Holiday Travel Gadgets for Geeks for Under $100
• Winter Holiday Food From Around the World