These are the times that remind travelers what airlines are supposed to do for their customers during what they refer to as "acts of God." They also separate the savvy passengers from the novices.

Most of the airlines spent yesterday trying to return to normal operations after the weekend's storm, with a majority saying they would be back to normal by today.

The storm couldn't have come at a worse time for the airline industry, which has lost more than $15 billion in the past two years. It was especially bad for Arlington-based US Airways, which is losing millions of dollars a day while restructuring in bankruptcy court.

US Airways was the hardest hit of the major airlines because it's the largest carrier in the Northeast. Since Saturday, the airline has canceled 1,500, or 40 percent, of its flights, affecting more than 500,000 passengers, said spokesman David Castelveter.

Most airlines encouraged travelers who have to change their reservations to use their Web sites to avoid long waits on the phone reservation lines or at airports. The wait on US Airways' reservation line has been 40 minutes to an hour.

Most major airlines, including American, United, Delta, US Airways, Southwest and AirTran, made the good-faith gesture of relaxing their standard $25 to $100 fees to make changes and re-booked passengers free.

Now, many airlines don't want you to know this, but under most of their policies, they must offer you the option of a full refund if a flight is canceled because of weather, especially if the carrier is unable to provide you with an alternative flight within a certain time.

Carriers often prefer to offer a voucher for a future flight or the option of booking a traveler on another carrier. But if those options aren't appealing, travelers should insist on a refund, regardless, if they are flying on a full fare or restricted ticket. "The refund won't necessarily be the first option, but it should be one of the options offered," said Norman A. Strickman, assistant director of the Transportation Department's aviation consumer protection division. Strickman's office polices airline policies on behalf of the public.

Travelers could have difficulty finding available seats at least through Friday. Many airlines are already near capacity, especially for early morning and late afternoon flights. Those seats are often sought by business travelers.

US Airways spokesman Castelveter said passengers will be able to find seats in several markets, but that in general, seats "will be hard to find."

AirTran, which canceled 125 flights from Saturday to Tuesday, hoped to have all of its stranded passengers on flights by tomorrow because most of its Friday evening flights are fairly full, spokesman Tad Hutcheson said.

Those passengers holding tickets with confirmed seat reservations or boarding passes often don't have to worry about getting bumped off their flight by a stranded traveler.

But Tom Parsons, chief executive of Bestfares.com, said travelers holding tickets could position themselves to get bumped off a flight and get a free ticket. To nab a free trip, Parsons recommends telling the gate agent before boarding that you would be willing to give up your seat in exchange for a free ticket or voucher.

"The airlines are going to be trying to accommodate more people during the next few days, which could put them in an oversell situation," Parsons said. "They're going to be pushing it to the limit to get people on their planes."

Savvy travelers have learned how to avoid all-night stays in airports. With most airlines, the passenger who was able to get through to a reservation agent the quickest is the one who often manages to wrangle a seat on the next available flight.

Terry Trippler, travel advocate at CheapSeats.com, suggested that if a flight is canceled, rather than waiting in line at a ticket counter, a passenger should quickly call the toll-free reservation number and make a reservation for the next flight out. For travelers in the airport, that may mean whipping out your cell phones before the phone lines get jammed.

"People who quickly make a reservation are often the first out of an airport," Trippler said. "Regardless if you're a million miler with the airline or a member of their airport lounge or have never flown the airline before, he who manages to nab a reservation, flies."

Biz Class on the Move: Remember, beginning Tuesday, Feb. 25, Business Class takes off on Tuesdays.