DALLAS >> Leading U.S. airlines are again trying to raise prices on many domestic flights.

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

US Airways confirmed that it raised fares on many U.S. routes by $6 per round trip, matching an increase by JetBlue Airways. 

Airlines have imposed about a dozen broad fare increases this year. Ticket prices vary by route, time of day, and whether they’re nonstop, and airlines often raise some fares while cutting others. This week, Southwest, American and JetBlue have run broad-based fare sales.