Summer Fare War Sparked by Northwest : Travel: Delta, American and United airlines quickly follow with special rates, which will still be higher than last year’s.

America’s biggest airlines slashed fares Friday as a battle for summer vacation travelers broke out among Northwest, Delta, United and American airlines.

The opening volley was fired late Thursday when Northwest, the nation’s fourth-largest carrier, announced discounts of as much as 33% on special summer fares to North American and some transatlantic destinations.

American Airlines, the nation’s biggest carrier, United Airlines and Delta Air Lines all followed suit in a matter of hours Friday.

“We have matched the Northwest fares,” said Tim Smith, a spokesman for American.

Delta said it would “definitely be very competitive in every market where we compete with Northwest.”

The move by Northwest essentially extends the time and routes of a similar sale announced last week by America West Airlines. The fare cuts can be a bit complicated because competing airlines are honoring both sales, which end on different days and apply to different routes.

Under the Northwest offer, tickets must be purchased by May 18 and travel completed between May 27 and Sept. 15. The non-refundable tickets require a Saturday night stay and apply to a limited number of seats. Prices are lower for off-peak travel on Tuesday, Wednesday and Saturday.

From Los Angeles, a round trip to New York--which normally sells for as low as $530--costs $418 for peak travel under the sale and $378 for off-peak travel. The promotional round-trip fare between Los Angeles and Dallas is $288 off peak and $328 at other times.

Deeper discounts of up to 33% are available for travel completed by June 30, Northwest said.

Even with the cuts, air fares this summer will be higher than a year ago, when airlines embarked on an even more aggressive fare-slashing bonanza--cutting fares by as much as 50%.

That fare war was also started by Northwest and produced among the biggest losses ever for the embattled airline industry. Wall Street analysts questioned the wisdom of financially strapped Northwest taking the first price-cutting step again during this year’s peak travel season.

The carrier has about $4 billion in long-term debt. It recently cut 1,000 jobs and canceled $6.2 billion in aircraft orders and options as part of a plan to raise $250 million in short-term cash.

But Northwest denied that the fare action was designed to quickly raise cash.

“This sale is designed to try to find a way to stimulate the market,” said Michael Levine, a Northwest spokesman. “This sale is not about raising cash.”

On Friday, the stock of American parent AMR Corp. fell $1 per share to $67.625, while Delta dropped $1.125 to $57.125, and United parent UAL Inc. fell 50 cents to $135.50. Northwest stock is not traded.