Major U.S. airlines are again trying to raise prices on many domestic flights.

Delta Air Lines Inc. confirmed Friday that it had raised fares to Florida, Phoenix and Las Vegas by up to $10 per round trip.

JetBlue Airways Corp. said that it raised fares on many U.S. routes by $6 per round trip, and US Airways Group Inc. said it matched JetBlue.

The fare hikes indicated that airlines are still seeing strong demand for travel despite the weak economy.

J.P. Morgan analyst Jamie Baker, who tracks airline prices closely, said a successful fare increase would help airline stocks, which have risen since American Airlines parent AMR Corp. filed for bankruptcy protection on Tuesday. Investors are betting that American will reduce flying, adding to revenue and profit at other airlines.

Airlines have imposed about 10 broad fare increases this year, but an equal number have failed because some carriers declined to go along with higher prices.

Ticket prices vary by route, time of day, and whether they're for nonstop flights. And airlines often raise some fares while cutting others. This week, American, Southwest Airlines Co. and JetBlue ran broad-based fare sales.