The BA news should not be seen in isolation. After a brief period in which analysts and traders hoped for a full-scale turnaround in the global airlines industry, those sentiments have faded. The dismay is reflected in the stock prices of US-based airlines. Shares of American (AMR) are down about 25 percent in the last month, and most stocks in the sector are off more than 10 percent.

The theory that airline earnings would get better was based on three premises, which have turned out to be largely untrue. The first is that fuel costs would continue to fall, or at least stabilize. The price of crude has risen to $80 and there are concerns that a step-up in the world’s economic growth will take oil even higher, bringing jet fuel costs with it.

Airlines have benefited from costs cuts, and that may continue, particularly if other large airlines follow BA’s example and cut more jobs. But carriers will eventually face the “car industry problem,” which is that there are only so many people who can be cut before firms starts to lose viability, and become unable to perform when business returns.

The last and most critical factor affecting airline earnings improvement is that many believed that the economic recovery would bring travelers out in droves. However, unemployment and a new frugality on the part of business have made it more difficult for airlines to draw passengers back, and that could be the case for another several quarters — if the economy continues to recover.

The notion that the business prospect of airlines is getting better is merely a notion.

“The last time Southwest Airlines offered airfares as low as $25 one way was 13 years ago,” said Tom Parsons, chief executive of BestFares.com. “This occurred during July 1996 for their 25th-anniversary sale.”

The July sale helped Southwest set monthly records for percentage of seats filled in August and September and probably will do so for October. In addition, while most competitors reported less revenue per seat mile flown in September, Southwest enjoyed a 3 percent increase in unit revenue despite the cheap fares.

“Southwest Airlines saw great success with our wild, 48-hour fare sale in July and wanted to offer even more discounts to customers,” said Kevin Krone, Southwest’s vice president of marketing, sales and distribution.

The response was so strong that customers complained on the airline’s Web site that they couldn’t get through to make reservations. At midafternoon, the Dallas-based carrier posted a message saying it thought the problems had been solved.

Other carriers selectively matched Southwest’s fares or lowered their existing fares in response. Fort Worth-based American Airlines Inc. initially offered some $39 fares in markets where Southwest had offered the $25 fares, such as Austin-Dallas, but American later lowered fares on some flights to $25.

“San Antonio, Houston, Austin, they’re all back down now to $25, matching Southwest dollar for dollar,” Parsons said. “They did the same thing in Chicago. They were $39.”

The sale fares, which must be purchased by the end of Thursday, were set at $25 each way for trips of up to 375 miles, $50 up to 549 miles, $75 to 999 miles and $100 for 1,000 miles or more.

Travel must be taken Dec. 2-16 or Jan. 5- Feb. 10 and not on Sundays. The prices do not include fees and airport charges.

While Southwest doesn’t charge for the first or second checked bags, most other airlines do, raising the prospect that a passenger could pay more for bags than for a ticket.

For example, someone with two checked bags flying round-trip on United Airlines Inc. between Chicago and St. Louis would pay $50 for their ticket, but up to $100 for the bags.

Parsons said a person flying round trip on Southwest between Dallas and Houston could fly for $50, but a little dog or cat carried onto the flight would cost $150.

Transport Minister Seiji Maehara may introduce legislation for a Japan Air turnaround plan that includes state-backed loans and pension cuts, Nikkei said, without saying where it got the information. The carrier, also known as JAL, is seeking government aid and debt forgiveness from lenders as it heads for its fourth loss in five years.

JAL is also considering selling a stake to AMR Corp.’s American Airlines or Delta Air Lines Inc. American, the world’s second-largest carrier, has proposed a deepening of ties with JAL as it seeks to keep the Tokyo-based airline in the Oneworld alliance, a person with knowledge of the plan said yesterday. Delta, the world’s biggest carrier, is a member of the rival Skyteam grouping.

Public broadcaster NHK also reported that JAL will seek support from the government-affiliated Enterprise Turnaround Initiative Corp. as early as today, without saying where it obtained the information.