At the Minneapolis-St. Paul International Airport on Tuesday, most travelers handily checked in for their flights and cleared security with few delays.

It was the calm — literally — before a major snowstorm, which is expected to hit the Twin Cities beginning this evening and snarl holiday travel.

The National Weather Service issued a winter storm warning Monday, with at least six inches of snow expected in the metro, across southern Minnesota and into west-central Wisconsin.

Wednesday is usually the busiest travel day before Thanksgiving, with up to 44,000 passengers expected to clear security at MSP's two terminals, according to the Transportation Security Administration (TSA). The average number of travelers screened is 36,800 a day.

Michael Anderson of Watertown, S.D., and family arrived in the Twin Cities the night before their flight to Phoenix on Tuesday. While he couldn't have predicted the impending snowstorm, Anderson was aware that the Tuesday before Thanksgiving is usually less frenetic than the day before the holiday.

"I've done this a few times," he said.

Nationally, some 31.6 million people are expected to take to the skies between Nov. 22 and Dec. 3, a nearly 4% increase over last year, according to Airlines For America, an industry trade group. Beyond Wednesday, Sunday is expected to be the busiest day, with 3.1 million people flying nationwide — a single-day record, if realized.

TSA said earlier this month that more than 26.8 million passengers will be screened at checkpoints nationwide between Nov. 22 and Dec. 2. That, too, is expected to break a record, TSA said.

For those holiday revelers hitting the road, AAA predicts they will be joined by more than 55 million travelers driving 50 miles or more this Thanksgiving. That would be almost a 3% increase over last year and the second-highest travel volume for Thanksgiving since the auto club began tracking in 2000.

Wednesday afternoon is predicted to be the busiest travel period nationally, AAA said.

"Strong economic fundamentals are motivating Americans to venture out this holiday in near-record numbers," said Paula Twidale, vice president of AAA Travel, in a news release. "Consumer spending remains strong, thanks to increasing wages, disposable income and household wealth, and travel remains one of their top priorities for the holiday season."

Rebecca MacDonald said she plans to drive from her home in south Minneapolis to a friend's house in north Minneapolis for Thanksgiving.

"We'd prefer to take transit, but the drive is 25 minutes and transit would take over an hour and include at least one transfer and about 20 minutes of walking," she said via Twitter.

With the storm looming locally, the Minnesota Department of Transportation said it has plenty of salt and 800 plows throughout the state to deal with the wintry onslaught.

The predicted snowstorm prompted MSP's dominant carrier, Delta Air Lines, to issue a weather waiver for flights to and from MSP Airport on Wednesday, meaning travelers can make a one-time change to their itinerary without paying a fee.

MSP's Skyway Checkpoint connecting Terminal 1 (Lindbergh) with the InterContinental MSP Airport Hotel was open Tuesday morning, after being shuttered due to low passenger volume. Officials with the Metropolitan Airports Commission (MAC), which owns and operates MSP, raised a ruckus about the closure with TSA, which relented last week and reopened it.

However, the MAC will end up paying for staffing there. The entrance will be open from 4:45 a.m. to 10 a.m. daily, accommodating hotel guests and other passengers with carry-on bags.

But the Skyway Checkpoint 10 at Terminal 1 was closed on Tuesday, due to an equipment issue, according to MAC Spokesman Patrick Hogan. Checkpoint 2 at Terminal 2 (Humphrey) remains closed due to staffing issues.

MAC officials will continue to press TSA to appropriately staff all checkpoints at the airport.

With different checkpoints closed at various times during the year "there were often too few screeners at the North and South Checkpoints [at Terminal 1] during key hours," Hogan said in an e-mail. "The TSA recently rebid screener shifts and now are opening more lanes in Terminal 1's North and South Checkpoints earlier than they have in the past, so that should help with ticketing lobby congestion at least."

Cliff Van Leuven, TSA federal security director for MSP Airport, said Skyway Checkpoint 10 was down Tuesday due to an airport power outage that knocked screening equipment out of service there. He expected it will be up and running later Tuesday.

In addition, the second checkpoint at Terminal 2 "is only open when there is sufficient demand to open it," he said. When it is open, TSA PreCheck passengers are routed there so all six lanes in Checkpoint 1 can be devoted to standard passengers.

MAC officials were advising travelers to arrive two hours before domestic flights, and three hours early for international trips.

Parking at the airport can be pre-booked through a new service,, ensuring travelers have a space when they arrive. Because business travelers tend to stay home during the holiday, the MAC doesn't anticipate any shortage of parking spaces.

The Quick Ride Ramp is an option for people with a lot of luggage who don't want to walk very far. The daily rate is $15 (compared with a daily rate of $26 for parking in ramps adjacent to Terminal 1). A shuttle bus picks up travelers at the ramp and delivers them to Terminal 1.

Delta has a new location for skycap curbside check-in at Terminal 1 off the upper east road opposite the main terminal's departure doors.

Tina Waltz was waiting Tuesday morning at Terminal 1 for her brother, who lives in St. Paul, to pick her up after flying in from Dayton, Ohio. She was aware of the oncoming snowstorm but undeterred.

"I brought my snow boots," she said. "I still make snow angels."