United and Continental airlines are raising fares on many U.S. routes by $10 per round trip.
The increase was confirmed Monday by Mike Trevino, a spokesman for the airlines.
U.S. airlines have raised fares at least a half-dozen times this year as they try to offset rising jet fuel costs. The last attempt failed when other airlines decided not to follow American Airlines when it raised prices earlier this month, also by $10 per round trip.
Rick Seaney, CEO of travel website FareCompare.com, said consumers also got a break last week when U.S. airlines offered more discount seats for early-summer travel. Still, he said, cheap seats will be harder to find this year.