Bankrupt U.S. carrier Delta Air Lines Inc. raised its ticket prices by $5 one-way on most domestic routes to offset high fuel prices, an airline spokeswoman said Wednesday.

Delta increased the fares Monday night for most of its domestic flights, including those serving Hawaii, Alaska and Caribbean markets, spokeswoman Betsy Talton said.

United Airlines, a unit of UAL Corp. (UAUA); American Airlines, a unit of AMR Corp. (AMR); and Northwest Airlines Corp. said they were studying Delta's fare increase. Continental Airlines Inc. (CAL) did not immediately respond to a request for comment.

U.S. airlines, including discount carriers such as JetBlue Airways Corp. (JBLU), have been raising fares to good effect on their bottom lines.

Several carriers reported profits in the second quarter despite record high fuel prices, thanks in part to a series of fare increases, fuller planes and a cut in domestic capacity.

However, slower demand in the upcoming autumn season could again put pressure on fare prices, and in what could be a sign of things to come, JetBlue Tuesday said it planned to lower fares by 18 percent to 34 percent on some seats on selected flights.

But for now, the latest fare increase by Delta is likely to be matched by other carriers, J.P. Morgan Securities' analyst Jamie Baker wrote in a research note.

"Given continued mid-East uncertainty and the reality of $74 crude -- and with scant evidence of consumer elasticity as fares push ever higher -- other carriers are likely to match over the next 48 hours," Baker wrote.