US Airways and Delta Air Lines Inc. are raising fares on many U.S. flights by up to US$10 per round trip, and other airlines are tinkering with prices too.

United and Continental raised the minimum prices they'll charge on sales and certain other fares, a spokesman said Thursday. The US Airways increase appeared to target business travelers.

The moves are the latest attempt by airlines to boost revenue during a normally slow time of year for travel. They succeeded in raising prices two weeks ago, but another fare hike last week fizzled and was eventually canceled.

US Airways Group Inc. confirmed Thursday that overnight it had raised fares by US$4 to US$10 per round trip. American said it was considering whether to match the increase. Southwest and JetBlue said they had not matched the increases.

Jamie Baker, an analyst for J.P. Morgan, said the US Airways price increases were on tickets favored by business travelers, including first-class and economy fares eligible for instant upgrade.

Airline officials have said that demand among corporate travelers has been holding up better than leisure travel because vacationers are more sensitive to small increases in price.

Airlines have been able to boost prices partly by limiting the number of flights and available seats. U.S. airlines have tried about 20 fare hikes this year, with half of them sticking. The others were rolled back, usually because some airlines -- typically a low-cost carrier such as Southwest or JetBlue -- declined to go along.

Higher fares helped most airlines earn money in the third quarter. Delta and United Continental Holdings Inc. earned more than US$500 million each in the third quarter, although American Airlines parent AMR Corp. and Southwest Airlines Co. lost money.