Updated

American Airlines (AMR), the nation's largest carrier, on Thursday largely matched the sweeping changes Delta Air Lines (DAL) made to its fare structure by eliminating Saturday-night stay requirements and lowering last-minute leisure and business fares in thousands of domestic markets.

Continental Airlines (CAL), Northwest Airlines (NWAC), United Airlines (UAL)and US Airways made more limited adjustments, copying Delta's cheaper ticket prices in select markets where they go head to head.

On Wednesday, Delta Air Lines Inc. cut its most expensive fares by as much as 50 percent and eliminated other restrictions in an effort to woo business travelers and other last-minute ticket buyers. Delta said no fare would be higher than $499 one-way in coach class or $599 one-way in first class under its new program.

Similar to Delta, America's parent AMR Corp. reduced the number of different fares in each market and sharply lowered the price of tickets purchased at the last moment — moves intended to appeal to business travelers who rely most heavily on so-called walkup fares.

For example, American said the price of a one-way, last-minute ticket from Dallas to Washington would drop to $499, down from $880. The highest fare between Chicago and Salt Lake City declined to $299 one-way, down from $524.

One analyst estimated that the fare changes, if mimicked by all other U.S. carriers, could reduce the industry's annual revenue by $2 billion to $3 billion a year.

On Wednesday evening American spokesman Tim Wagner confirmed "broad changes to our fares." Two discount carriers, Southwest (LUV) and AirTran (AAI), said they already offer lower fares than Delta's new model.

AMR shares were down 30 cents, or 3.3 percent, at $8.75 a share in afternoon trading on the New York Stock Exchange, where shares of Delta shares were down 18 cents, or 2.6 percent, at $6.62.

Continental Airlines Inc.'s stock fell 76 cents to $10.45 on the NYSE, while Northwest Airlines Corp.'s stock slipped 28 cents to $8.32 on the Nasdaq Stock Market.