ATA is offering an introductory fare starting at $255 one-way or $413.50 round-trip with a five-day stay when it launches its daily, nonstop Honolulu-Seattle route on Feb. 20.

Hawaiian's round-trip fare on that date with a five-day stay is $854.76.

It's too soon to tell if there will be a price war.

Hawaiian doesn't plan to match ATA's low fare, said Mark Dunkerley, president and chief operating officer of Hawaiian. But Hawaiian will keep a close watch over the no-frills carrier and may alter its fares if ATA grows its market share, he said.

When a low-cost carrier captures 10 percent of a market, fares tend to come down, Dunkerley said.

ATA, the nation's 10th largest carrier, now has 8 percent of the Hawai'i market, and that could go up a percentage point or two when its new service begins, Dunkerley said.

"We do recognize ATA is attempting to grow, and we will meet that competition," Dunkerley said. "We will have to look at what ATA does and determine where we need to be regarding price points, which isn't the same thing as having the cheapest fares."

Dunkerley is confident Hawaiian's customers will remain loyal to the company.

"We are quite bullish about our ability to fill the airplanes," Dunkerley said.

ATA added its Honolulu-Seattle route to meet customer demand, said Angela Thomas, ATA director of corporate communications. ATA will be the only low-cost carrier offering nonstop service to Seattle from Honolulu.

"Hawai'i is underserved by low-cost carriers, and ATA fits that bill," Thomas said.

ATA and Hawaiian are also competing on their San Francisco and Los Angeles routes.

In 2003, ATA carried 434,000 passenger seats, an increase of more than 15 percent over a year earlier, according to Hawai'i Visitors & Convention Bureau analysis based on the Official Airlines Guide.

In the previous year, ATA had 376,510 passenger seats, a decrease of more than 4 percent from 2001. After the Sept. 11 terrorist attacks, traffic across the airline industry plunged as travelers avoided flying.

Since 1994, ATA has flown scheduled flights to Hawai'i for tour packager Pleasant Holidays.

ATA, a subsidiary of ATA Holdings Corp., said its highest one-way fare from any of its Mainland cities to Hawai'i will always be less than $600. The airline charges $50 to change a flight unlike the $100 fee charged by most major carriers.