Millions of holiday travelers heading to the nation's airports over the next week can take some solace: Neither the Christmas nor Thanksgiving travel seasons are the busiest of the year, a USA TODAY analysis shows.

Airports are crowded and hectic this time of year, but much of the perception about holiday air travel is wrong, according to the analysis, which ranked daily flight data from the Bureau of Transportation Statistics (BTS) and the Federal Aviation Administration.

Flight volumes are lower during the holidays than peak days in summer, and delays are usually less severe, data show.

Darryl Jenkins, an airline consultant, said the idea that the holidays are the busiest air travel time of the year "has been conventional wisdom for as long as I can remember."

Not only are there more flights during the summer, but several airlines reported the number of passengers per plane is higher then as well, Jenkins said.

Holiday air travel, the 2006 data show, does not crack the year's top 20 busiest days.

"Make no mistake, they are very busy days," says American Airlines spokesman Tim Wagner. "But we have busier days in the summer, and we have more of them."

Last year, the Thursday and Friday before Christmas — Dec. 21 and 22 — ranked as the 23rd and 24th busiest air travel days of the year with 20,761 and 20,760 flights, respectively, according to the BTS.

The airlines' official schedules for 2007 show a similar trend, according to OAGback Aviation Solutions, which tracks global airline data.

Nov. 22, 2006, the Wednesday before Thanksgiving — considered the busiest day of the year — ranked as the 36th busiest, according to the BTS. Its 20,686 flights were 201 fewer than the busiest day of the year, Friday, Aug. 4, 2006.

One holiday in 2006 beat both Christmas and Thanksgiving. The Friday before Labor Day ranked 14th for most flights.

The bottom line: taking a flight on virtually any Thursday or Friday during the summer is worse. Seats are just as packed, there are more flights, and there is a greater likelihood of being delayed, due primarily to thunderstorms and volume.

Travel experts warn that holiday travelers are still susceptible to severe weather that can wreak havoc on the aviation system.

Last year, a massive snowstorm hit holiday travelers in the days before Christmas. On Dec. 22, 64% of flights did not arrive on time — the worst day for delays that year, according to the BTS.

Meanwhile, airlines are predicting 2.5 million people will take flights on the four peak days this holiday season: Wednesday, Jan. 2; Friday, Dec. 21; Thursday, Dec. 27; and Wednesday, Dec. 26.

Contributing: Barbara Hansen