A first-class seat selling for less than coach? Sounds like a traveler's dream -- or a cruel hoax.

Some passengers are in fact finding seats in the front of the plane for prices that should have landed them back with hoi polloi. Many carriers -- seeking to fill the entire plane -- are heavily discounting first-class seats on competitive routes.

"It's a chance to grab some market share or perhaps steal a customer from another airline," said American Airlines spokesman Tim Smith.

Travel experts say airlines discount their first-class fares in an effort to get revenue for a seat that might otherwise be filled by a passenger who upgraded with frequent flier miles.

"It's a way to get a little more money out of a seat that you might not otherwise get," said Heather Dolstra, vice president of District-based Democracy Travel.

The first-class fares are not selling below the price of a discounted coach seat. Rather, Dolstra pointed out, the cheap first-class seats are generally priced less than full, last-minute fares in coach. Obviously, a bargain hunter can find cheaper fares with more restrictions, such as advance purchase and minimum stay requirements.

For example, a walk-up, round-trip, first-class seat on US Airways from Washington to Los Angeles International Airport was available recently at $2,003, while a full-fare coach ticket on the same flight was $3,085.

Northwest Airlines had a $1,313 round-trip, first-class fare from Washington to Seattle, with a coach seat on the same flight selling for $2,378.

Delta Air Lines offered a $521 first-class fare to Atlanta and an $822 coach seat on the same flight.

Before you scramble for a first-class fare, beware: You have to be quick -- even lucky -- to find one. The seats are particularly scarce from the outset because, of course, there are many fewer first-class seats than coach on every flight. And many of the first-class seats come with a raft of restrictions. For example, they may require an advance purchase or a minimum night stay.

Continental Airlines spokesman David Messing said the cheaper fares are a result of aggressive discounting by the airlines. "It's not a common occurrence, but it is conceivable," he said.

Northwest Airlines spokesman Kurt Ebenhock said that as the coach section fills up, some airlines may discount the first-class cabin.

"Just as there are a variety of discounted coach fares, there is more than one first-class fare as well as a number of discounted business-class fares internationally," Ebenhock said. "If a traveler is talking to reservations or a travel agent, they should ask for lowest coach fare and lowest first-class fare and compare the two."

Persistence is key, but even if business travelers find a dream fare, they may not be allowed to use it because their company travel policies may prohibit booking a first-class seat.

Michael H. Sommer, a Jacksonville, Fla.-based marketing consultant, found a $512 fare to Los Angeles on Continental Airlines over the Memorial Day weekend by using the airline's toll-free reservation system. Although the fare was lower than the $900 coach fare he found on the same flight, Sommer bought the more expensive ticket. The reason: His client would not have approved of paying for a first-class ticket, no matter what the ticket price.

"I would have had a lot of explaining to do," Sommer said. "My client would not have understood and would have thought I was abusing their generosity."

A business traveler might be able to get approval for a first-class fare if the passenger provides a written statement from a travel agent that the fare was lower than the available coach fare.

For passengers who own their companies or have greater flexibility in their travel purchases, cheaper first-class fares might be just the ticket. But frequent fliers trying to upgrade their way into first class may not be quite so happy; they may have to accept that the odds may be longer now for them to nab a seat up front.

JetBlue Teams with American Express: JetBlue Airways and American Express Co. announced plans yesterday to issue a co-branded charge card within the next month.

It will be American Express's first co-branded card with a U.S. airline since it teamed with Delta in 1995.

JetBlue American Express cardholders will be able to earn one mileage point for every dollar spent. In addition, travelers will be able to earn bonus points when they use their card depending on the type of purchase.

Details of the program, as well as the card's annual fee, won't be announced for another month, executives said.

JetBlue chief executive David G. Neeleman said eight banks approached the airline in hopes of creating a co-branded credit card. The card will be another source of revenue for the airline since American Express pays JetBlue whenever a cardholder redeems their frequent flier points for a free trip.

With many carriers struggling, few companies are rushing to the airline industry for marketing relationships. But Al Kelly, group president of American Express U.S. consumer and small-business services, said JetBlue has established a "loyal customer base" which it believes should translate into a "successful relationship."