Thanksgiving week is morphing into an air-travel nightmare, and the airlines already have their built-in excuse: The weather stinks. You name it, we're getting it this week—rain, snow, fog, and sleet are pounding the nation's key hub airports, and the Federal Aviation Administration's delay map is blinking with every "danger" color in the bureaucratic palette.

What is it about Thanksgiving that has made it the worst travel period of the year? It's a perfect storm of demand, timing, inexperience, and weather.

Start with demand: From early on the Monday morning before Thanksgiving through late into the Sunday night afterwards, most of America is on the move. Song and story may claim that we go "over the river and through the woods" to Grandmother's house, but that was back in the days of nuclear families and 50-cent-a-gallon gas. These days, we all fly to Grandma's—or Uncle Phil's or Cousin Sue's. Planes are packed every day of the holiday week, and statistical wonks predict that as many as 5 percent more Americans will be flying this year than in 2006.

Then there's timing: Everyone needs to be someplace on Thursday. Not Wednesday evening or Friday morning, but Thursday. Unlike almost all of the other secular or religious holidays we celebrate, Thanksgiving applies to all Americans on exactly the same day. If you ain't at the table on Thursday, you've blown the holiday. And frankly, the nation's creaky airlines, airports, and air-traffic-control system are at their least efficient and most unappealing when the entire country is demanding same-day delivery.

Worse, everyone is an inexperienced traveler during Thanksgiving week. The seen-it-all, done-it-all, know-it-all business travelers that I write for in Seat 2B are actually (and blissfully) at home. Thanksgiving travel is about harried families, unaccompanied minors, and befuddled seniors overloaded with gear and carrying too much of what the Transportation Security Administration has deemed contraband. If it's not teenagers slowing down the security lines with their high-top, lace-up sneakers, it's that adorable grandma who hasn't flown since 1976 and didn't know that 42-ounce bottles of shampoo no longer pass muster. None of these folks get the carry-on rules, the checked-bag regulations, or the A.T.M.-like ticketing procedures that dominate airports today. And with airlines employing about 200,000 fewer workers since September 11, there's no one at the airport who can enlighten the uninformed or lighten their load.

Finally, there is the weather. It's not uniquely bad this year. It is late November, and the weather is always bad somewhere in late November. It could be fog in L.A. or a freak snowstorm in Denver or just a cold, driving rain in Chicago or Dallas. And it always throws a meteorological monkey wrench into Thanksgiving week.

Happy Thanksgiving—and let's hope you're not making do with a turkey sandwich from the airport food court tomorrow.