Holiday flights are pricier this year, and domestic round trips for Thanksgiving average $402, up 31% from last year, Hopper data show. Christmas trips average $452, up 23%. Both are 10-year highs, USA Today reported.

Fuel is a big reason. Jet fuel prices are high, and Spirit Airlines shut down in May, taking seats out of the market, ABC News reported, citing Katy Nastro of the flight app Flighty.

The calendar matters this year, because Thanksgiving falls on Nov. 26 this year. Kayak says Thanksgiving fares usually hit bottom about five weeks before the trip, which means booking before the end of October. Hopper also advises booking before Halloween. Expedia's data point to Nov. 5 as the last good day to book domestic Thanksgiving flights, and Oct. 15 for international ones.

For Christmas, Expedia says to book domestic trips by Nov. 10. Kayak finds Christmas fares often dip four to seven weeks out.

Your travel days can save money too. Flying on Thanksgiving Day can cost about 19% less than flying on Friday, Nov. 20, the most expensive day, Kayak says. Expedia suggests leaving Monday, Nov. 23. The Sunday after the holiday, Nov. 29, is the priciest day to fly home, with fares up to $604, ABC reported. For Christmas, Dec. 18 to 20 is the peak.

A few more tips can help. Booking two one-way tickets instead of a round trip saved about 29% on domestic trips in Kayak's data. Morning flights are less likely to be delayed, ABC noted. Points and miles can also help with peak-season fares, the CEO of the travel site Going told USA Today.

Here's the history. Thanksgiving and the end-of-year holidays are the busiest stretches for U.S. air travel, and airlines often set records in those weeks. Fares tend to rise as seats fill, so travelers who wait until November often pay the most.

Know your rights: Under federal rules, airlines must give a cash refund if they cancel a flight or change it significantly and you choose not to travel.

What we know: Thanksgiving and Christmas fares are at 10-year highs, and booking windows close over the next few weeks.
What we don't: Whether fuel prices will ease enough to bring fares down before the holidays.