Fuel is the highest airline cost, accounting for about a quarter of expenses. That is down from a high of 35 percent during the oil price run-up two years ago.

"The legislation has the potential to be a multi-billion-dollar benefit to this industry," James May, chief executive of the Air Transport Association, told Reuters.

Most airlines, including American Airlines, United and Delta, hedge a portion of fuel expenses but the volume and price differ. Contracts, which lock in prices, are a bet on commodity markets that crude or jet fuel prices will go up or a strategy for ensuring stable costs, even at a higher level.

A provision in the measure signed by President Barack Obama limits the size of trades, or futures contracts, for anyone not hedging with the intent of taking delivery of fuel.

Most big carriers are significantly reducing their hedge positions for 2011.