DALLAS — Led by Delta Air Lines Inc., most major carriers cut leisure fares on flights through Dec. 12, although the deals don’t apply to the busiest days around Thanksgiving and may sell out quickly.

The timing of the fare sale caught analysts off-guard, coming just over a week after Delta and American Airlines raised fares on most of their U.S. routes.

“It is a good deal, and if you want to get away between now and Dec. 12, I recommend people check it out,” said Terry Trippler, who tracks the airline industry for myvacationpassport.com. He said the sale applied to the lowest booking class and will sell out early.

Trippler noted that the fare sale is only temporary, while increases, such as the $10 per round trip boost of a week ago, are permanent.

Neil Bainton of farecompare.com said the sale prices, which Delta filed in ticketing systems Sunday, applied to 7-day advance-purchase tickets.

Bainton calculated the average reduction at $281, which he said was a surprisingly deep cut. He said many represented new lows on specific routes.

Among the fares Delta listed were $158 round trips between New York and West Palm Beach, Fla., and between Atlanta and Dallas; and $238 between New York and Seattle and between Atlanta and Las Vegas.

The sale does not include Nov. 22, 25 and 26 — the Wednesday before and the weekend after Thanksgiving Day. Those are heavy travel days, and airlines hope to sell out those flights without offering lower fares.

American — a unit of AMR Corp. — Continental Airlines Inc., UAL Corp.’s United Airlines, Northwest Airlines Corp., US Airways Group Inc. and JetBlue Airways Corp. said they matched the fare sale on Monday. Two weeks ago, Southwest Airlines Co. launched a sale through March, but the Dallas-based carrier cut some fares again to match Delta, said spokeswoman Beth Harbin.

Julie King, a spokeswoman for Houston-based Continental, said the sale applied to most markets in the United States and Canada. The sale fares require an overnight stay, she said.

On Nov. 2, American and Delta imposed a broad $10 per round trip fare increase on business and leisure fares. The increase was matched by most other U.S. carriers.

U.S. airlines have enacted nearly two dozen widespread fare increase in the past two years, according to analysts. Airlines say they need higher fares to cover the cost of jet fuel.