For the traveler who wants or needs to fly, the bargains have arrived -- and others are undoubtedly on the way as airlines scramble to fill empty seats by offering sharp discounts in air fares.

For three days last week, several U.S. carriers waged an air-fare war, selling tickets for future travel at half price, and more discount promotions are expected in the weeks ahead. Today, British Airways is launching what it calls a "no-risk" fare for summer travel to Britain at 33 percent off its normal advance-purchase ticket price. Passengers who change their minds can get a full cash refund up to 14 days before departure. Other international carriers could match the offer.

Airline passenger numbers have tumbled both because of the recession and the continuing threat of terrorist attack resulting from the Persian Gulf War. Transatlantic travel has been particularly hard hit because of Europe's perceived vulnerability to terrorist dangers and the weak dollar in relation to major European currencies.

"The fact is, advance bookings are very soft," says Bill Jackman of the Air Transport Association of America, which represents U.S. carriers. "And airlines are trying to get rear ends into those seats." Pan Am spokesman Alan Loftin notes, however, that the airline saw a slight improvement in passenger loads last week to its key markets in London and Frankfurt.

The price cuts are occurring despite the prediction that U.S. carriers will lose more than $750 million in the first quarter of this year, a figure cited by Jackman. Last week's surprise fare war, launched by America West in the face of such a gloomy outlook, even has some airline spokespersons perplexed.

"Having people on a plane doesn't mean you're making any money," says Nancy Vaughan of USAir. On the other hand, a full plane even at discount prices can help reduce the total amount of the losses.

The America West fare war abruptly ended a move by Northwest to impose a $15 round-trip surcharge on air fares, which it had hoped to begin collecting last Friday. Apparently most other carriers decided that slashing prices rather than raising them was going to attract more passengers.

One bright spot for the airlines is that the cost of fuel, which prompted multiple fare increases in recent months, has dropped. Before Iraq invaded Kuwait in August, Delta Air Lines was paying about 57 cents a gallon for fuel, says spokesman Neil Monroe. By the time the war broke out, the cost had surged to $1.20 a gallon. Now it's back to about 77 cents a gallon. The lower fuel price gives airlines more flexibility in reducing fares, at least for the time being.

U.S. airlines also have trimmed staffs and eliminated some flights, mostly to Europe and Asia, as a way to reduce operating costs. The big question facing them now is how to convince people to travel while the war rages and the terrorist threat continues. Lower fares may be one answer.

Although the half-price offers expired yesterday, unadvertised discounts are still available to many destinations. For example, Delta currently is offering 20 percent off its normal fares to "walk-up" customers in many of its East Coast markets, including Washington. And until March 15, says Monroe, travelers can get a 30 percent discount on three-day advance-purchase tickets that are fully refundable. There's a 65 percent discount for a three-day advance-purchase ticket, if you stay over a Saturday night.

Unlike the U.S. air industry, international air travel remains government regulated. As a result, airlines cannot raise or lower fares as easily or quickly. British Airways' new promotion is subject to approval both by the U.S. and British governments. They often grant it, but not in every case.

Nevertheless, the British Airways offer may be what travelers can expect for transatlantic flights this summer. The airline has reduced its regular round-trip, 30-day advance-purchase fare by one-third. To qualify, you must book and purchase the ticket before March 15 for travel between April 6 and Oct. 31.

To convince travelers to buy now, the airline has waived normal cancellation penalties. If you decide not to go, you can obtain a full cash refund up to 14 days before the departure date. If you cancel within 14 days, you will get a voucher good for future travel on British Airways within a year.

Air fare discounts, of course, are nothing new to the industry. Over the years, the airlines have come up with a variety of ways price-conscious passengers can trim the cost of a flight within the United States or abroad. If you cannot qualify for some of the current promotions, you might be able to take advantage of one of these:

Advance-purchase discounts: Almost the only people who buy costly full-fare tickets are business travelers who don't qualify for advance-purchase discounts. American and foreign airlines substantially reduce fares to passengers who are able to plan and buy tickets ahead -- often 30 days before departure. Most carriers limit the number of low-cost seats on each flight, so the earlier you book, the better chance you have of getting one. These tickets usually carry restrictions. Many are not refundable if you cancel, and you have to pay a penalty if you change the itinerary. Also, you may have to stay over a Saturday night or a minimum of seven days.

Senior and student discounts: Most U.S. airlines offer special discounts to older and younger travelers. For example, Delta Air Lines sells special coupon booklets to travelers 62 and older. A booklet of four coupons costs $472, and one coupon is good for a one-way trip anywhere in the continental United States. At this price, the most you would pay for a transcontinental round trip is $236 using two of the four coupons. Delta collects two coupons each way for travel to Alaska and Hawaii. But at $472, the fare is still a bargain, especially from the East Coast. For even greater savings, a booklet of eight coupons is $792. However, all the coupons must be used within one year of purchase.

Off-season travel: International fares tend to drop during slack travel periods, and especially to Europe from mid-October to mid-March. This winter, the Washington-Frankfurt fare has been about $400; during the peak travel period of mid-summer, the price in a less-troubled year might be expected to jump to almost twice as much. If chancy weather doesn't intimidate you, winter is the cheapest time to fly to Europe.

Special promotions/air-fare wars: U.S. airlines regularly offer special air-fare sales on domestic routes, most often during slow travel periods; such sales usually are announced in large ads in metropolitan newspapers. One airline's special promotion may prompt other carriers to follow, and a brief air-fare war erupts. You have to keep watch for the ads, because these sales may last only a few days. If you don't act quickly, you lose out.

Since international air fares are regulated by intergovernment agreement, airlines can't raise or lower them at will. As a result, incentives to attract international travelers normally are in the form of discounts on lodgings and car rentals abroad. Occasionally, an airline opening a new route will promote it with discounted fares.

Air/lodging packages: If price is important, independent travelers headed for a resort destination should look into packages that combine air fare, lodging and perhaps a rental car or transfers from the airport. Packages are put together by tour operators booking in volume, and generally they are cheaper than what you might pay if you tried to do it on your own.

Off-peak fares: Lots of business travelers fly Monday morning and Friday afternoon, so fewer discounted seats are available then. You have a better chance of a cheap fare if you can fly midday, mid-week or overnight on a red-eye flight. Most travelers prefer to fly nonstop, but fares often are cheaper if the flight makes a couple of stops. Ask a reservation clerk or travel agent for the least-expensive departure time and routing to your destination.

Consolidators/"bucket shops": In the United States, we call them consolidators; abroad, they are known as "bucket shops." Their specialty is selling international air fares at a bargain. Through a quirk in international fare regulations, they are able to obtain seats in volume at fares not available to individual travelers. You can ask most travel agents to book a consolidator fare from the United States or check the international air fare ads in Sunday newspaper travel sections. Travel ads in foreign newspapers can direct you to "bucket shops" abroad. Consolidator tickets carry restrictions, and you may travel on unfamiliar airlines. The best deals currently are for travel to Asia and South America.

Charters: Tour operators generally put together charter flights to popular destinations during peak vacation times, such as to the Caribbean in winter and to Europe in mid-summer; often lodging packages are alsoavailable. In effect, the tour operator is renting a plane for the flight to and from your destination. In addition, some charter airline companies, such as Martinair-Holland -- a subsidiary of KLM Royal Dutch Airlines -- offer regular weekly service from U.S. cities to Europe in the summer. Martinair will fly from Newark to Amsterdam, beginning in the spring. Charter fares are almost invariably cheaper than fares on scheduled carriers, but there are drawbacks. For example, most round-trip flights are only once a week, so you can't use your charter ticket to fly home early if the need arises. Contact a travel agent for information about charters to specific destinations.

Hidden market: Two hidden markets in cut-rate airline tickets are currently active. Participating in the markets is not against any U.S. law, but the airlines are opposed. If they find you trying to use a hidden-market ticket, they probably will confiscate it.

One market operates through the classified ads in many metropolitan newspapers. Under the "Tickets" heading, individuals sometimes offer free coupons won in airline promotions or try to unload a nonrefundable ticket they are unable to use. The nonrefundable tickets generally carry a specific departure and return date, and you may have to travel under the name of the seller. Tickets generally are for travel within the United States.

The other hidden market is operated by coupon brokers, who buy excess frequent-flier miles from travelers who have earned more than they can or want to use and then sell the mileage coupons at a big discount. Most of the brokers' business is in first-class tickets on international flights. For a list of brokers, contact the American Association of Discount Travel Brokers, 85 S. Union Blvd., Suite G300, Lakewood, Colo. 80228.

Rebate travel agencies: These are no-frills agencies for travelers who know when and where they want to fly. You phone in the specifics, and the agency quotes you the lowest price. For this service, the agency charges a fee, but it then rebates its sales commission to the client. Travel Avenue of Chicago (800-333-3335), a leading rebater, charges a fee of $8 per person to handle the sale of a domestic airline ticket, and it returns a 7 percent to 12 percent commission, depending on the airline.

Courier services: Some travelers are able to fly on sharply discounted tickets by serving as couriers for freight companies. The drawback is that you must fly on the date when a courier is needed and to a specific destination. You generally must pay at least part of the cost of the ticket, although the price is usually much lower than for a regular air ticket. And you must stay abroad for a specified period, usually a week or two, to be able to return as a courier. Couriers can take only carry-on luggage; the shipment being transported abroad goes as your checked baggage.

Now Voyager (212-431-1616) is a New York clearinghouse for courier flights.

Standby fares: Some international airlines offer reduced-price standby fares during peak travel periods. In recent years, for example, British Airways has promoted them on flights from Washington-Dulles International to London during the summer.

You may not know if you are going to travel until the day of the flight, but you fly at a good price for the season.

Frequent-flier bonuses: If you are a frequent traveler, you should collect miles whenever possible for all your flights, hotel stays and car rentals.

Pan Am has been advertising triple miles to some destinations, which is a quick way to earn free tickets. And through April 30, the Hilton Hotels chain is offering triple mileage credit to United and American airline passengers who charge their stay on a Visa card.

Some airline-affiliated bank cards also help you build mileage points at the rate of one point for every $1 you spend. The mileage points can be exchanged for free flights for individual or family vacations. You won't fly any cheaper.

Bereavement fares: If you have to fly because of a serious illness or sudden death in the family, always ask if the airline has a bereavement fare. Otherwise you might have to pay a full fare.

Some carriers have established special fares, while others may waive advance-purchase requirements. In either case, you save a lot of money. To qualify, you may have to produce verification from a doctor or funeral home.

Air passes: Many foreign airlines sell air passes for unlimited travel within a single country or region. In Australia, for example, Ansett and East-West airlines are offering "Explore Australia Airpasses" that take 30 to 40 percent off regular economy fares, according to Ansett.

LIAT, a Caribbean airline, markets a pass good for travel at a reduced rate over its routes to numerous islands. If you plan extensive air travel within a country or region, check with the national tourism office for information about air passes.

Security Advisories

The State Department has issued a new advisory warning that the threat of possible terrorist actions in the eastern Mediterranean -- including Greece and Turkey -- has increased and is expected to continue throughout the war.

"In Turkey and Greece together," the advisory says, "there have been more than a dozen terrorist attacks, targeting the property of organizations with official and commercial ties to the U.S. and other countries allied against Iraq." The advisory urges Americans to use caution when traveling in the eastern Mediterranean. A separate advisory for Turkey, issued earlier, advises U.S. citizens to defer all nonessential travel to southeastern Turkey until the war is over.

An updated advisory for Jordan advises Americans to defer all travel there because of "increased tensions." U.S. citizens living in Jordan have been advised to depart as quickly as possible. For the latest advisories, contact the Citizens Emergency Center, 202-647-5225. In addition, travel agents have access to travel advisories on their computer reservation screens.