SEATTLE — Capt. Mike Adams demonstrated what the future will look like at the nation’s airports as he pulled back on the throttles of his Boeing 737 flight simulator, setting the engines on idle to glide smoothly from his cruising altitude all the way down to the runway.


Starting in June, that’s exactly what actual Alaska Airlines flights will be doing when the airline begins testing the use of satellite technology to land at Seattle-Tacoma International Airport — all in the hope of saving fuel and reducing delays.


Alaska Airlines, one of the nation’s smallest airlines, has taken some of the biggest steps in adopting a technology that allows its planes to navigate Alaska’s hazardous terrain, weaving through narrow valleys and mountain peaks, and land at remote airports in some of the worst imaginable weather. It now wants to demonstrate that the same technology can also work at big, busy airports, said Captain Adams, the airline’s chief technical pilot.


Planes using the new technology will cut 30 miles from their approach to the airport by taking a more direct path to the runway. They will no longer need to circle overhead awaiting clearance to land. And pilots will not have to push and pull at the throttles — in effect, repeatedly stepping on the gas, then coasting — to maintain the altitude assigned by air traffic controllers as they begin a stairlike descent. For passengers, landing will feel more like coming down a slide.


“This makes much better use of the airspace,” Captain Adams said “It improves efficiency and reduces congestion. That’s the holy grail we’re all aiming for.”


The Seattle experiment marks one of the first extensive applications of satellite technology after years of planning and political wrangling in Washington.


Replacing the radar-based air traffic control system, which the nation’s airports have relied on since the 1940s, is an enormous and expensive undertaking. By one official government estimate, the price tag could reach $42 billion by 2025.


But the agency in charge of the program, the Federal Aviation Administration, has been hamstrung by political infighting that deprived it of a stable budget for five years. Congress finally approved a four-year budget for the agency in February, including $1 billion a year for the program, called the Next Generation Air Transportation System, or NextGen.


The program has already been beset with trouble. A government audit found in February that half of the 30 critical contracts needed to build the new system were delayed, and more than a third were over budget.


And the airlines complain that the F.A.A. has been slow to create new landing procedures that make the most use of satellite guidance. It takes five to 10 years to create these procedures because of lengthy environmental and noise impact studies, and the difficulty of coordinating flights in busy airspaces. The F.A.A. is now trying to speed up that process to three years.


The agency has approved tests using satellite-guided landings at Phoenix Sky Harbor International Airport, and experiments are planned this year in Washington, D.C.; Atlanta; Charlotte, N.C.; and Dallas. Delta Air Lines, Southwest Airlines, JetBlue and American Airlines have all been trying out various aspects of satellite navigation.


Given the expected growth in air traffic in the next decades, airlines and regulators say there is an urgent need to modernize the existing air traffic control system. The F.A.A. projects that the number of planes flown by domestic airlines will double in the next two decades, while the number of domestic passengers will reach 1 billion by 2024, up from about 732 million this year. Much of that growth will be concentrated in the biggest airports, most of which are already congested, particularly at peak hours. 


Radar has proven to be reliable over the years. But air traffic controllers can be sure of the precise location of the planes they are directing only when their radar sweeps once every six seconds. To make up for that uncertainty, controllers keep wide buffer zones between flights. Satellite technology will eventually change that equation and allow planes to fly much closer to one another because they will broadcast their locations with more accuracy.


In effect, airports could increase capacity without building more runways because more planes could take off and land every hour.