Updated

Last-minute business travelers and some first-class fliers will pay more this summer for domestic tickets on some of the major airlines.

Some fares at the major airlines have been creeping up in recent months largely because of persistently high fuel prices.

Delta Air Lines Inc., the nation's third-largest carrier, has raised one-way domestic fares on unrestricted first-class and walk-up coach tickets by $50, spokeswoman Chris Kelly said Thursday. Other first-class tickets were not affected.

Wednesday's move by Delta was quickly matched by United Airlines and American Airlines, according to spokespersons at the two carriers.

Industry analyst Jamie Baker said in a research note that US Airways also matched the increase, though an official there did not immediately return a call Thursday seeking confirmation of that. Northwest spokesman Kurt Ebenhoch said his airline is studying Delta's move, while a Continental representative did not immediately return a call seeking comment.

At Delta, the airline also has raised its most expensive one-way fares on domestic coach and first-class tickets to $699 and $799, respectively. Kelly stressed that the prices are not a cap, though she wouldn't say if that means they could go even higher.

"In a dynamic fuel environment, we must be flexible and be able to respond to increasing costs while maintaining a competitive cost structure," Kelly said.

The airline's most expensive one-way domestic and first-class fares have now increased $200 since Delta announced its SimpliFares program in January 2005. A key element of the program was caps on those two classes of fares at $499 and $599, respectively. Kelly said other elements of the program, including a simpler fare structure, cheaper ticket change fees and fewer restrictions, have not changed.

She said the fares being increased at Delta represent less than 5 percent of its domestic tickets.

Shares of Elk Grove Village, Ill.-based UAL Corp. (UAUA), United's parent, rose $1.25, or 4.5 percent, to $29.06 in early afternoon trading Thursday on the Nasdaq Stock Market. Shares of Fort Worth, Texas-based AMR Corp. (AMR), American's parent, rose $1, or 4.6 percent, to $22.88 in trading on the New York Stock Exchange, where shares of Phoenix-based US Airways Group Inc. rose $1.89, or 4.5 percent, to $44.38 and shares of Houston-based Continental Airlines Inc. rose $1.18, or 5 percent, to $24.80.

Atlanta-based Delta and Eagan, Minn.-based Northwest Airlines Corp. are operating under bankruptcy protection, and their shares are traded over the counter.