PHOENIX — Your ginger ale doesn't come in a glass anymore on most US Airways flights. On Delta you'll find yourself in a thinner, lighter seat.

With jet fuel prices so high, airlines have no choice but to scour their planes for ways to lighten the load. There's no room for even the smallest bits of dead weight, from redundant wing lights to extra wires in the walls. Manufacturers also are using lighter materials in plane construction.

"The pressure is immense" to cut weight, said John Heimlich, chief economist for the Air Transport Association of America, an industry trade group. "Every penny more per gallon adds $195 million to the industry's expenses per year.

"You simply cannot make all of that up with fare increases."

Jet fuel, which the Energy Department's Energy Information Administration tracked at $3.17 per gallon in New York last week, has doubled since the beginning of 2007. It outpaced labor as the biggest airline expense three years ago. As of September 2007, fuel made up 27 percent of operating expenses for U.S. airlines, according to the latest data from the Bureau of Transportation Statistics.

The industry has struggled to keep up. Carriers have increased fares, cut capacity, parked their gas-guzzler planes, charged customers to check a second bag, trimmed staff and pushed as many passengers as possible to automated kiosks.

Carriers have pulled out unused ovens, magazine racks and trash compactors during the past few years. Some removed paper manuals in the cockpit and installed electronic maintenance logbooks.

Fort Worth, Texas-based American Airlines created a Fuel Smart Team in 2005 as fuel prices started to go up. Tom Opderbeck, American's manager of strategic programs, said the team tried to cut weight in places that customers wouldn't notice.

The team capped electrical outlets in the lavatories and cut the power converters from the wall. It took out phones in seat backs and removed the heavy telephone wiring that was folded inside.

The weight-savings measures were unrelated to the grounding this week of MD-80 planes operated by American, a company spokesman said yesterday. American and Delta Air Lines both had to cancel flights after Federal Aviation Administration inspectors questioned whether the airlines had properly performed a modification. A $10.2 million civil penalty imposed by the FAA on Southwest Airlines this month also was unrelated to fuel-saving measures.

Last year, American replaced its silverware on business and first class with another set that was made from a lighter metal.

Tempe, Ariz.-based US Airways had similar ideas when it redesigned aircraft interiors after its 2005 combination with America West Airlines.

Sherri Shamblin, US Airways vice president for InFlight Services, said management realized it could save fuel by simply replacing meal carts with ones that weigh 12 pounds less.

"Twelve pounds is significant when you run anywhere from six to 35 carts on an airplane," Shamblin said. The lighter carts will save the airline $1.7 million a year in fuel costs, she said.

Management decided last month to continue to lighten its meal service by getting rid of glassware on domestic flights. Its East Coast flights already had switched to plastic. But on western flights previously run by America West, first-class passengers were still handed beverages in glass flutes and tumblers, Shamblin said.

A lot of airlines are also trying to fly differently to be more fuel efficient. They're carrying less water and putting less gas in the tank if the plane doesn't need it to make the trip. They also plug in planes to ground power as soon as the plane lands.

Southwest Airlines cut fuel costs simply by flying more direct routes. The Dallas-based carrier equipped planes with life vests during the past two years, allowing pilots to fly over bodies of water and shave miles off their flights.

All of these changes have helped airlines boost their fuel efficiency, Heimlich said. But he's not sure how much more fuel conservation airlines can do. As fuel prices continue to rise, he said, carriers are parking many of their planes and cramming customers into the remaining flights.

"The place to cut now is simply the quantity of service: The number of flights, the number of seats," he said. "In other words, the only thing left to cut is the amount of supply itself."