Some Long-Haul Air Fares Slashed : Travel: America West triggers latest cuts in coast-to-coast rates. Savings of more than 50% offered on some routes.

The nation’s airlines Monday slashed discount air fares by more than 50% on some major coast-to-coast routes through mid-June.

The most recent price cut, which was started by America West Airlines and matched by most other major carriers, will prove popular with leisure travelers, particularly around the Easter and spring break holidays, travel agents said.

The America West sale applies to a limited supply of seats in about a dozen long-haul markets, two of which include Los Angeles. A Los Angeles-New York round trip costs $318, while a Los Angeles-Boston round trip costs $328. Before the sale, the lowest discounted round-trip fare to both cities was $659.

The sale ends March 10 and travel must be completed by June 15. The non-refundable tickets must be purchased two weeks in advance and require a Saturday night stay.

“It’s a pretty good deal,” said Thomas Nulty, president of Associated Travel Management in Santa Ana. During the same period last year, the sale price of a Los Angeles-New York round trip was $50 higher, he said.

A sale “will stimulate traffic anytime you get down to the $300 range for travel to the East Coast,” Nulty said.

Most major carriers--including American, Delta and United--matched America West on competing routes.

America West also announced a second sale, which applies to a larger number of destinations but cuts discount fares by no more than a third. That sale, which expires March 30 and is good for travel through June 15, is an extension of a promotion the Phoenix-based carrier has been offering for more than a year.

Under the one-third-off sale, the price of a Los Angeles-Atlanta round trip falls from $566 to as low as $418 for travel on Tuesdays, Wednesdays and Saturdays. Fares are higher on other days.

Both sales come as several carriers said their advance bookings through June are running ahead of last year. “Things are looking a little bit better than they have in the past,” said Marty Heires, a spokesman for American Airlines. “It’s one of the signs of an improving economy.”

Before the string of America West sales, coast-to-coast discount air fares had risen above $600. “They’ve gotten pretty high,” said Marilyn Hoppe, vice president of revenue management at America West. “These fares at the lower levels will hopefully stimulate a little more traffic.”

The airlines’ more costly regular discount fares and the constant fare sales result in more travelers than ever waiting for the next promotion before buying a ticket, travel agents say.

Nulty said he is asked the same question by clients and acquaintances: “When is the next sale coming?”