Air travel is so safe you'll probably never have to use any of the advice we're about to give you. But if you ever do need it, this information could save your life. Airline passengers usually take safety for granted when they board an airplane. They tune out the crew's pre-flight announcements or reach for a magazine instead of the cards that show how to open the emergency exit and what to do if the oxygen mask drops down. Because of this, people are needlessly hurt or killed in accidents they could have survived. Every time you board a plane, here are some things you should do:

* Be reasonable about the amount of carry-on luggage that you bring. FAA rules require airlines to limit the amount of carry-on baggage, and if you try to carry too much with you, the crew may insist that you check in some items. (There is no universal limit; it depends on the aircraft type and the passenger load.) A bag that is not properly stowed could turn into an unguided missile in an accident or block the aisles during an evacuation.

* Be careful about what you put into the storage bins over your seat. Their doors may pop open during an accident or even a hard landing, spilling their contents. Also, passengers in aisle seats have been injured by heavy items falling out of these compartments when people are stowing or retrieving belongings at the beginning or end of a flight. Please be considerate of others and put hard, heavy items under the seat in front of you; save the overhead bins for coats, hats, and small, soft bags.

* As soon as you sit down, fasten and unfasten your seat belt a couple of times. Watch how it works. There are several kinds of belts, and in an emergency you don't want to waste time fumbling with the buckle.

* Before take-off, there will be a briefing about safety procedures, pointing out emergency exits and explaining seat belts, life vests and oxygen masks. Listen carefully and if there's anything you don't understand ask the flight attendants for help.

The plastic card in the seat pocket in front of you will review some of the safety information announced by the flight attendant. Read it. It also tells you about emergency exits and how to find and use emergency equipment such as oxygen masks. As you're reading the card look for your closest emergency exit, and count the number of rows between yourself and this exit. Remember, the closest exit may be behind you. Have a second escape route planned in case the nearest exit is blocked. This is important because people sometimes head for the door they used to board the plane, usually in the front of the first class cabin. This wastes time and blocks the aisles. Oxygen masks aren't the same on all planes. Sometimes they drop down in front of you. On some aircraft, however, you'll have to pull them out of a compartment in front of your seat. In either case, you must tug the plastic tube slightly to get the oxygen flowing. If you don't understand the instructions about how the mask works, ask a flight attendant to explain it to you. When the plane is safely in the air and has reached its cruising level, the pilot usually turns off the "fasten seat belt" sign. He or she usually suggests that passengers keep their belts buckled anyway during the flight in case the plane hits rough air. Just as seat belts should always be worn in cars, they should always be fastened in airplanes.

If you are ever in an air accident, you should remember these things:

* Stay calm.

* Listen to the crew members and do what they say. The cabin crew's most important job is to help you leave safely.

* Before you try to open any emergency exit yourself, look outside the window. If you see a fire outside the door, don't open it or the flames may spread into the cabin. Try to use your alternate escape route.

* Remember, smoke rises. So try to stay down if there's smoke in the cabin. Follow the track of emergency lights embedded in the floor; they lead to an exit. If you have a cloth, put it over your nose and mouth.

After an air accident, the National Transportation Safety Board always talks to survivors to try to learn why they were able to make it through safely. They've discovered that, as a rule, it does help to be prepared. Avoiding serious injury or surviving an air accident isn't just a matter of luck; it's also a matter of being informed and thinking ahead. Are you one of those people who jumps up as soon as the plane lands, gathers up coat, suitcase and briefcase, and gets ready to sprint while the plane is still moving? If so, resist the urge. Planes sometimes make sudden stops when they are taxiing to the airport gate, and passengers have been injured when they were thrown onto a seat back or the edge of a door to an overhead bin. Stay in your seat with your belt buckled until the plane comes to a complete halt and the 'fasten seat belt' sign is turned off. Never smoke in airplane restrooms. Smoking was banned in all but the designated smoking sections after an accident killed 116 people in only 4 minutes, apparently because a careless smoker left a burning cigarette butt in the trash bin. There is a penalty of up to $2,000 for disabling a lavatory smoke detector. Also, don't smoke in the aisle. If there is a sudden bump you could stumble and burn yourself or another passenger. Lit cigarettes have also flown out of passengers' hands and rolled under seats.