Once or twice a week, airplanes landing at the UPS transport hub in Louisville, Ky., chart a new course to the runway. Using the latest in GPS tracking technology, the planes glide toward their destination in a maneuver called a "continuous descent," which brings planes to the ground on a direct line, rather than through a gradual approach.

New aircraft maneuvers rarely make news, but UPS's testing of the new technique in Louisville, Sacramento, Calif., and Cologne, Germany, could substantially reduce skyway congestion, noise, and pollution—and save money on jet fuel costs. Recent testing at Hartsfield International Airport in Atlanta found that each continuous-descent landing saved 1,300 pounds of carbon dioxide.

With oil costs soaring, every drop of jet fuel counts. Eight years ago, passenger and cargo airlines in the United States had a fuel bill of some $16 billion. This year's bill will approach $60 billion, experts predict. Last month, the cost of fuel increased about 69 percent from a year ago, according to the Air Transport Association. Total fuel costs for UPS for all its vehicles, including planes, through the first quarter of 2008 was $950 million, up 54 percent from last year. Starting on July 7, the company will impose an additional fuel surtax of 32.5 percent per package, up from the current 28 percent. Passenger airlines have begun charging passengers for carry-on baggage; start-up airlines are going bust, and smaller cities—more than 30 last year—are seeing their service cut, all because of fuel costs.

In January, the Federal Aviation Administration gave UPS, the world's largest package carrier, the green light to begin testing the new landing procedure at the Louisville facility, which handles some 100 cargo planes per night. One or two of those flights a week use the new technique, says Mark Giuffre, a UPS spokesman in Louisville. Tests over the past few months indicated that each landing using the continuous descent system saves an average of 50 gallons of jet fuel, or about $200 per flight. "That adds up, especially these days," says Giuffre. Indeed, the company estimates it will save $400 million on jet fuel costs each year for its entire fleet of planes.

In a traditional landing, pilots glide the plane through a series of predetermined elevations in their approach to the runway. This practice makes noise and uses more fuel as planes rev their engines to level off at each of the elevation intervals. Think: moving down a series of steps.

With continuous descent, the airplane relies on GPS guidance to essentially coast on idle in a direct line from its cruising elevation to the tarmac. Think: sliding down a ski slope.

The GPS system that makes continuous descent possible is part of the FAA's Next Generation Air Transportation System, nicknamed NextGen, which also enables planes to fly in straight lines rather than following the twisting paths of the current radar-based system—another fuel saver. In addition, NextGen allows planes to fly closer together, land more planes in quicker succession, and be rerouted more quickly. With some 7,000 planes aloft over the country at any one moment, the new system should also ease congestion and flight delays. The FAA has approved allowing continuous descent tests in Los Angeles, Phoenix, and Salt Lake City.

But the GPS systems aren't cheap. Every plane needs reprogramming of its onboard computers and other systems, putting the cost to refit some older planes at $300,000. There are ground GPS units too, though at $200,000 per unit (several are needed for each airport) they are still a bargain compared with million-dollar radar units.

While the FAA and trade groups estimate that NextGen could reduce fuel consumption by more than 10 percent, it is unlikely to be in place until 2025 because of cost and technology issues. Meanwhile, Congress and the airlines are still bickering about who will foot the bill for the new system, expected to cost perhaps as much as $20 billion to implement. The airlines are clamoring for tax credits and subsidies to offset the cost. Legislation to address the problem has stalled in Congress and probably won't be addressed for months.