New Air Fare War Started by TWA With 2-for-1 Offer : Travel: Most other airlines are selectively matching the struggling carrier’s promotion, which expires Saturday.

The nation’s airlines plunged into another major--albeit brief--fare war Thursday, offering two tickets for the price of one during the upcoming fall and winter months.

The 2-for-1 sale was launched by Trans World Airlines and expires Saturday. Two can travel on a Los Angeles-New York round trip for as little as $461 combined. Before the TWA sale, the lowest round-trip fare offered by major airlines on the same route was $376 for one traveler.

Jim M. Roberts, president of Uniglobe Regency Travel in Rancho Cucamonga, said one client who was traveling to Hawaii alone on business ended up buying a second ticket for his wife. Both will now travel on TWA for a total of $324 round trip.

“He couldn’t believe it,” said Roberts.

Most other major airlines--including American and United--selectively matched TWA’s promotion, which includes most types of unrestricted and discount fares and travel on all its domestic and European routes.

Under the TWA promotion, two people traveling together must purchase the tickets at the same time and take the same flight. Domestic travel must take place between Sept. 15 and Jan. 31, 1994. European tickets apply to flights between Nov. 1 and March 31, 1994.

Northwest, Continental, America West and USAir matched the promotion only on domestic routes where they compete with TWA. United Airlines said it will offer the 2-for-1 deal only on discount tickets that must be purchased two weeks in advance.

American Airlines--the nation’s largest carrier--said its promotion also will apply only to two-week advance-purchase tickets and will exclude trips that begin or end in Dallas or Chicago. In addition, American will match the TWA promotion on flights to Continental Europe but not the United Kingdom.

Last summer, American, in response to a similar 2-for-1 promotion kicked off by Northwest Airlines, decided to cut all discount fares in half during the peak summer season. Airplanes were jammed all summer long, and the carriers posted huge losses as a result of the money-losing sale.

However, industry observers said that this time, the limited nature of the sale will limit the damage. The promotion covers what is typically the slowest time of year, a period when discounts are not uncommon. In fact, airlines are currently engaged in a 35%-off sale for late-summer and early-fall travel.

In addition, the restriction will make it difficult for business people--who often travel alone and at the last minute--to take advantage of the promotion. “Business people rarely make their plans that far in advance,” said Thomas Nulty, president of Santa Ana-based Associated Travel Management.

The sale will help TWA, which emerged from Chapter 11 bankruptcy protection earlier this week, to attract travelers who have avoided the carrier in favor of larger carriers with newer aircraft.

“Some percentage of the passengers will stick with them in the future,” said Donald S.Garvett, an airline pricing expert at Simat, Helliesen & Eichner, a New York consulting firm. “It’s smart marketing.”