For domestic flights, a driver's license or other government-issued photo ID is all you need to show at check-in, security and boarding. However, under the new Western Hemisphere Travel Initiative, travelers flying to Canada, Mexico, Bermuda, Central and South America, and the Caribbean will need to present a passport as of January 23, 2007.

For domestic flights, you should be at the airport at least 90 minutes before your flight is scheduled to leave if you're planning on checking luggage.If you're bringing just a carry-on, allow at least an hour.

If you're flying to Hawaii, the U.S. Virgin Islands or an international destination, arrive at least two hours early. During peak travel times, allow even more time at the airport -- perhaps an extra 30 to 60 minutes. Check with your airline for its recommended arrival times, as these may vary depending on where you're flying. For instance, American Airlines suggests allowing three hours for flights to Mexico and a whopping 3.5 hours for flights to Delhi, India.

Before you leave for the airport, call your airline or check its Web site to see if your flight is leaving as scheduled. Keep in mind that airlines are not required to compensate passengers for delayed or canceled flights. Each carrier differs in its policy, and there are no federal requirements. Most will book you on the next available flight. If your plane is delayed, the airline may pay for meals or a phone call, so ask.

Some will offer no amenities if the delay is caused by bad weather or other conditions beyond their control. Compensation is required by law only if you are bumped from a flight that is oversold (discussed below). Although it is not required by law, many airlines are beginning to inform passengers to the causes for delays in their flights, through their own programs.

Beware: Even if you have already checked in for your flight, an airline can cancel your reservation if you are not at the departure gate on time. Even if you have an advance boarding pass or an advance seat assignment, your seat may be given to another passenger. Similarly, if you do not check your baggage in sufficient time for it to be loaded on your flight, the airline is not responsible for any delay in the delivery of your baggage to your destination

Overbooking is legal, and most airlines do it. They are, however, required to ask people to volunteer to be bumped. If you are bumped involuntarily, you must be given a written statement describing your rights and explaining how the carrier decides who gets on an oversold flight and who doesn't, and you may keep your ticket and use it on another flight.

If you choose to make your own arrangements, you can request an "involuntary refund" for the ticket. You are also entitled to compensation, with a few exceptions. For example, if the airline arranges substitute transportation that is scheduled to get you to your final destination (including later connections) within one hour of your original scheduled arrival time, you get nothing.

If your bags are delayed, airlines usually agree to pay "reasonable" expenses until they're found. The amount is subject to negotiation, and you may have to fight for it. If your bags are not found, you must file a claim, which takes some time to process. It is normal to wait six weeks to three months for reimbursement, although some airlines are much more efficient than others.