Airlines that pay for their jet fuel when they fill up their planes have been forking over more than $2 a gallon lately - nearly four times the average price they were paying just four years ago.

High fuel prices have dealt a much milder blow to carriers that have used a practice known as fuel hedging, which most often involves purchasing futures contracts that allow airlines to fix or cap the price they'll pay several months or years in advance.

Southwest Airlines Co. has led the pack, followed by Seattle-based Alaska Air Group Inc., the parent company of Alaska Airlines and Horizon Air.

Both companies are bracing to pay market rate for more of their fuel in the coming years after ramping down their hedging programs as persistently high oil prices sent the cost of those futures contracts soaring.

But now, with some experts predicting that crude oil could creep up another $10, $20, even $30 a barrel, some airlines are taking cautious steps toward hedging again.

"The idea is to spend some money now to avoid the harm that would happen to our business if fuel went up by a significant amount," said Brad Tilden, Alaska Air's chief financial officer.

Some airlines hedge against jet fuel prices, which have averaged about $2.17 a gallon over the past three months - up from an average of about 55 cents a gallon in 2002. Others base their contracts on the price of crude oil, which has been trading above $70 a barrel since spring, compared to an average of less than $15 a barrel in 1998.

"You're basically buying a level of certainty," said John Heimlich, vice president and chief economist for the Air Transport Association. "The market price may be higher, it may be lower, but I know what I'm going to pay, and I can set my business plan accordingly."

In the last several years, Southwest has reaped sweeter rewards from fuel hedging than any other airline in the industry - nearly $1.8 billion in savings from 1999 to 2005.

Seven years ago, the Dallas-based low-fare carrier set a goal of having most of its projected fuel consumption hedged, said Laura Wright, the company's chief financial officer.

One of the most common types of fuel hedging contract is known as a "call option" or "cap," which names the highest price an airline would have to pay for fuel, usually averaged over a future monthly or quarterly period.

"If fuel prices drop, well, we're out the premium we paid," said Steve Rock, manager of Alaska Air's fuel hedging program. "If prices go above the $75 barrel threshold, we would start getting compensated back for whatever quantity we purchased at that level."

Hedging became difficult, if not impossible, for some airlines during the industrywide slump that followed the Sept. 11, 2001, terrorist attacks.

Whether companies are hedging fuel, aluminum, coffee beans or Japanese yen, they generally need to have good credit and be in a position to pay some substantial upfront costs. That's been an obstacle for carriers that have had to limp through bankruptcy reorganization.

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