Dallas ? A fresh round of airfare cuts are great for travelers but pose a continuing problem for older airlines that can’t make money at such low prices, analysts say.

Shares of many carriers fell Tuesday after JetBlue Airways announced it was putting 1 million seats on sale for up to half-off this fall, including $99 one-way fares from New York or Boston to cities in California.

Other low-cost carriers also have cut fares in recent days, putting more pressure on older airlines.

“It’s just a little fall fare sale,” JetBlue chief executive David G. Neeleman said. “The other airlines will all match it. It’s good for the consumers.”

But the cost will be especially high for older, so-called legacy carriers, who analysts said would be forced to match the fare sales.

JetBlue’s price cut and a sale from Frontier Airlines came one week after Southwest Airlines introduced one-way sale fares from $39 to $99 for late summer and early fall. AirTran also has cut some fares as low as $44 one way.

Tom Parsons, publisher of travel Web site Bestfares.com, said the current price war was unusual in its breadth — that with so many low-cost carriers offering discounts at the same time, “80 percent of America is on sale.”

Pricing power in the industry has permanently shifted from the big airlines, which used to be able to drive out upstarts, to the low-cost carriers that can thrive at lower prices, he said.

The older airlines, such as United, American and Delta, are saddled with higher costs for labor and planes and have suffered huge losses since 2001.

Delta Air Lines Inc. announced Tuesday that it would take a second-quarter charge of $1.65 billion to cover deferred income taxes and pilots’ pensions. Also, Smith Barney Citigroup downgraded AMR Corp., the parent of American Airlines, the largest U.S. carrier, saying rivals who restructured could wind up with lower costs.

The combination of news sent airline stocks lower. Delta shares fell 66 cents or nearly 10 percent, to close at $6.09 on the New York Stock Exchange. Shares of AMR fell 42 cents or 4 percent, to $9.93.