DALLAS — Southwest Airlines Co. has joined a sweeping increase of $10 in the price of many domestic round-trip airfares, citing the need to offset high fuel prices.

Southwest's action over the weekend may have ensured success for a price hike by major airlines that seemed to be faltering. Southwest carries more U.S. passengers than any airline and wields great influence over prices.

It's the sixth time airlines have raised fares already this year. FareCompare.com CEO Rick Seaney says leisure travelers may now have to pay $260 for a ticket that cost $200 back on Jan. 1.

The airlines say they need the money.

“Fuel prices are up every week and the fare increases aren't keeping pace with fuel cost increases,” Southwest CEO Gary C. Kelly told The Associated Press.

Kelly said Southwest is on pace to spend $1.3 billion more on fuel this year than last year. That's nearly triple the airline's $459 million net income for 2010, or about $15 per customer.

WASHINGTON — Consumers borrowed more in January to purchase new cars but were once again frugal with their credit cards, offering a mixed sign of their confidence in the economy.Borrowing rose 2.5 percent, or by $5 billion, the Federal Reserve said Monday. It was the fourth consecutive monthly gain.Strong car sales drove the increase. The category that includes auto loans rose 6.9 percent.But credit card debt fell 6.4 percent in January — the 28th decline in 29 months — to lowest level since September 2004. Americans had increased their use of plastic in December for the first time since the financial crisis. But they cut back the following month, even though a Social Security tax cut is giving most households an extra $1,000 to 2,000 this year.