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United last week raised fares by $4 to $30 round trip, citing record fuel costs. Other carriers matched that increase. No major airlines immediately matched the airline’s latest increase across their route networks.

“My gut tells me that this attempt may not make it,” Chief Executive Officer Rick Seaney said.

Mr. Urbanski said adjusting the fuel surcharge, which is typically wrapped into the final price customers see when they buy tickets online, rather than the base fare, gives the airline more flexibility to respond to changes in fuel prices.

But Joe Brancatelli, who runs the business travel Web site, said the strategy has another benefit for airlines: “They put on surcharges instead of raising fares so corporations — who pay the most for tickets anyway — don’t get their corporate discounts.”

Jet fuel prices, which are rising with the price of oil, jumped to an average of $3.26 a gallon in New York through March, up 73 percent from a year earlier.

That difference is significant, given that an Airbus A320 or similar mid-size jet burns about 6 gallons of fuel per seat per hour, said airline consultant Robert Mann. Older planes and regional jets consume even more fuel.

The surge in fuel prices has left airlines scrambling to find ways to boost non-ticket revenue by charging extra, not just for drinks and food, but also for baggage and added leg room .

Still, raising ticket prices is the surest way to boost revenue, so carriers are likely to continue pushing fares higher even if United’s latest increase is eventually rolled back.