A March storm that caused hundreds of canceled flights at Dallas/Fort Worth International Airport and later cancellations related to equipment inspections are good reminders to travelers to know what to do if a flight is canceled.

Due to severe weather, American Airlines shut down all of its flights in and out of D/FW for the safety of passengers, crews and planes. The only other time this many planes were diverted was Sept. 11, 2001.

Later, Southwest and American grounded some planes at D/FW and Love Field for safety checks.

D/FW is a hub for American, so incidents affected not only Dallas-area travelers, but also connecting passengers in other cities.

If American had not canceled flights, there would have been more trouble. Travelers connecting in Dallas would have been diverted to other airports and jets would have been scattered around the country because of these diversions.

There probably would have been an issue for pilots at the end of the month, too. Pilots cannot fly more than a certain number of hours per month, and if the planes were scattered about, the situation would have eaten up some of that time, leaving the airline short of pilots at month's end. For example, Northwest had to cancel many flights last summer because its pilots ran out of hours.

Each airline has a contract of carriage, which states what its responsibilities are, including when there is a delay or cancellation.

Weather falls under "force majeure," which American defines as weather, acts of God, war and other conditions.

American's contract states "AA may, in the event of a force majeure event, without notice, cancel, terminate, divert, postpone or delay any flight or the right of carriage or reservation of traffic accommodations without liability except to issue an involuntary refund."

In this circumstance, travelers are not entitled to anything except a refund, although, in practice, the airlines will put you on a later flight.

If your flight is canceled due to something within the airline's control, such as a mechanical problem, the airline is not required by law to offer you compensation, but many do. What each airline offers is spelled out in the contract of carriage.

If you have a lengthy delay, ask for meal vouchers. And if you are stuck overnight, also ask for a hotel voucher.

Look at the airline's contract of carriage online before you depart, so you know what the terms are. You may want to print out the section on cancellations and delays so that you have the information if you need it at the airport.

When flights are canceled, the airlines' computer-reservations systems automatically assign new flights for passengers, but they may not be the flights you want.

If your flight is canceled and you are already in a long line at the airport, use your cellphone to call reservations, or go online if you have a laptop.

If you call and the agent can't accommodate what you want, call again and see whether another agent can.

Severe weather can have repercussions thousands of miles away.

It is a good idea to check your flight status before you leave for the airport, even if the sky is clear.

I sign up for e-mail or cellphone flight notification so I can be informed of a change or cancellation.

Also check the weather online, on the radio or on television. If it looks as if severe weather is headed your way and you can be flexible, see whether you can change your flight.

When you are at the airport and there is a delay, be kind to the gate agents. When something goes wrong, you can bet that they've had a worse day than you have, and they are the ones who can get you on another flight.

If you feel you are not getting the service you should be getting, request a supervisor. If you remain calm and polite throughout the experience, you are more likely to get a satisfactory response.

Tom Parsons is publisher of Bestfares.com.