United Turns Up Heat in War for West Coast Fliers : Airlines: Competitors are likely to match the carrier’s new triple-mileage bonus program.

United Airlines stepped up the dogfight for passengers in the hotly contested Los Angeles-to-San Francisco air corridor Wednesday by announcing triple-mileage bonus incentive programs aimed at frequent business travelers.

The announcement promises to set off a new round of bonus offers among airlines vying for a share of more than 2.5 million passengers a year, analysts said.

“Everybody is out there to get a presence,” said Lee R. Howard, chief executive of Airline Economics Inc., a Washington-based consulting firm. The first airline with a major promotion usually gains market share, he added.

United, whose parent company is the object of a union-led buyout effort, said it will award triple miles to members of its Mileage Plus frequent-flier program who travel between Los Angeles and San Francisco. The bonus program, retroactive to April 7, will run through Dec. 31.

The program also awards miles for certain other flights and, under certain conditions, includes a quadruple-mile bonus for flights between the San Francisco Bay Area and the Northwest.

“United Airlines has made the strongest commitment in its history to California and the West Coast,” Jack Pope, United’s executive vice president for marketing and planning, said in a statement.

Competitors in the corridor were considering late Wednesday whether to match United’s program.

But, said William Berry, spokesman for Delta Air Lines in Atlanta: “You can be assured we will not allow ourselves to be at a competitive disadvantage.”

Competition in the corridor has intensified recently, with some airlines flying more frequently, offering deeply discounted fares and offering mileage incentives at the same time that others are cutting the number of seats available.

Delta and Southwest Airlines, both of which had relatively few intra-California flights, have significantly expanded their service on the corridor. Southwest fueled the competition frenzy in April with a cut-rate $59 one-way fare between Burbank and Oakland.

With 27 half-hourly flights per day between Los Angeles International Airport and San Francisco, United is already one of the top three carriers in the corridor. Earlier this year, it went to half-hourly flights between Los Angeles and San Francisco from 7 a.m. to 7 p.m.

The leader in the market, USAir, said its current bonus mileage program is more generous than United’s new offer, though it does not contain a triple- or quadruple-mileage provision.

The other top carrier, American Airlines, said it is studying United’s program. American already offers double miles for flights in the corridor.

Delta, which said it had not had a chance to review United’s offer, also offers double miles.

Analysts worried that the United program would revive widespread use of triple-mileage incentive programs. Introduced nationally by Delta in 1988, they were quickly matched by other airlines. They proved costly when airlines were forced to give away an unexpectedly large number of free trips.

“The potential liability from such programs is substantial, (though) we don’t know at this point what it is,” said one industry analyst. “So any return to the triple-mileage program (in the California corridor) has the possibility of spreading to other markets as well.”

The concern is especially salient in California, one of the most competitive markets in the nation. Few airlines make much money in the state, despite heavy traffic.

Other details of United’s program:

* Fliers earn double miles for nonstop flights from the San Francisco and Los Angeles airports to any non-corridor destination in the United States.

* Fliers earn triple miles for flights between San Francisco or Oakland and Portland or Seattle, beginning with the third flight. They can earn quadruple miles beginning with the ninth flight. The offer is good through Aug. 31.

* After 10 corridor flights, a frequent flier will earn double miles on all domestic non-corridor flights that originate or end in one of seven California airports--San Francisco, Oakland, Los Angeles International Airport, Burbank, Long Beach, Ontario or Orange County.