Air fares are up dramatically this holiday season — so there’s no point in waiting for last-minute deals because they’re not going to happen, experts say.

“You have a lot more pent-up travel demand chasing fewer seats,” said Rick Seaney, chief executive of Farecompare.com. “There’s just no incentive for airlines to lower fares.”

The days of cheap holiday plane tickets are over, he said. Airlines have been cutting capacity in the last couple years in response to lower demand.

Opinions differ as to the severity of the fare increases. Genevieve Shaw Brown, senior editor for Travelocity, said domestic air fares are higher by 5 percent for the December-January season, averaging $421 round trip. She said that international flights are up by 11 percent, for a round-trip average of $894.

Seaney’s estimate is much higher. He said that fares are up by 17 percent for the December-January season from last year. He based that calculation on 1,200 routes through the 50 busiest airports in the U.S.

Seaney said the increase is so dramatic because air fares are recovering from a 2009 bottom caused by slumping demand from the ongoing recession.

Air fares and travel volume are also higher for the Thanksgiving holiday, according to forecasts. The Air Transport Association forecasts an increase of 3.5 percent in travel volume for the Thanksgiving period from last year. AAA said that Thanksgiving air fares are up 4 percent from 2009.

As a result of the lower capacity and packed flights, Brown of Travelocity said the old trick of holding out for last-minute deals no longer applies. Airlines are unlikely to have empty seats, she said.

“Over peak holiday travel, it doesn’t make much sense to roll the dice and wait to book your tickets,” she said. “It’s just very unlikely that prices will drop over a high demand period. It’s really just in your best interest to book as far ahead as possible for the holidays.”