United Airlines and Continental Airlines have increased fares as much as $50 per round trip fare to help make up for higher fuel costs. The airlines' move, the fifth attempt to boost prices since January, came as the price for jet fuel hit a record $3.21/gallon last week, according to government statistics.

The airfare increase is the largest single domestic fare hike since the Sept. 11, 2001, terror attacks, the San Francisco Chronicle reported Saturday. "Three-dollar-plus jet fuel does not make cheap fares economically viable," said Henry Harteveldt, an airline analyst at Forrester Research in San Francisco. Every $1 increase in the cost of a barrel of crude oil means almost $470 million in additional expense to the U.S. airline industry, Elizabeth Merida, a manager at the Air Transport Association, told the Chronicle.

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