Those are the changes the Federal Aviation Administration has been promising for years through an ambitious program to modernize the nation’s air traffic system, and replace radars on the ground with satellite technology. The problem is that this new system, called NextGen, will cost an estimated $30 billion to $42 billion to complete. So far, the airlines have been reluctant to put up their half of the money for a system that will not be operational for at least a decade.

But NextGen, which stands for the Next Generation Air Transportation System, received a boost on Friday with House passage of a $59.7 billion bill that finances the F.A.A. over the next four years, providing much-needed stability to the agency’s flagship program. Since 2007, the F.A.A. bill had been repeatedly stalled and its budget temporarily extended 18 times.

The bill, which was approved 223 to 196, largely along party lines, also cuts overall spending on aviation by $4 billion and includes a provision that would curb the right of airline employees to unionize. The bill from the Republican-dominated House must still be reconciled with a vastly different version that the Senate, controlled by Democrats, approved in February. The White House has said it will veto a final bill that includes the labor provision.

And Representative Nick J. Rahall of West Virginia, the ranking Democrat on the House Transportation and Infrastructure Committee, assailed the deep cuts in the F.A.A. budget, which, he noted, came a week after two airliners landed at Washington National Airport without being able to contact the single air traffic controller on duty.

Modernizing the nation’s current air traffic system, which is based on technology invented during World War II, is universally seen as critical to coping with the congested airspace over the United States and to accommodate growing traffic. In its latest forecast, the F.A.A. estimated that United States airlines would carry 1.3 billion passengers in 2031, up from about 700 million in 2011.

Just like GPS for cars, satellite navigation gives pilots their exact location at any given time. Air traffic controllers would not have to wait 30 seconds for the next sweep of their radar screen to know the locations of planes. Radar’s limits means that controllers must now keep planes three miles apart when they approach airports. This limits the number of planes that can land each hour and contributes to the longer lines for takeoff.

“Today’s airspace is woefully antiquated,” said Steve Fulton, who helped pioneer satellite-guided navigation with Alaska Airlines in the 1990s and now works for GE Aviation.

Airlines burn an extra 10 percent of fuel today, he said, as they circle complicated approach routes or are put on a holding pattern by controllers juggling several flights.

“Instead of a chaotic and unplanned and unpredictable system, NextGen would provide precise synchronization,” he said.

Because of the surge in traffic in recent decades, the current system is often operating at the limits of its capacity. Robert W. Mann Jr., an aviation industry expert in Port Washington, N.Y., estimated that delays and airport congestion cost the industry as much as $12 billion a year in lost time and extra fuel costs.

The United States has also been lagging other countries that are already moving into this digital navigation age, including Australia, Canada, China, and several European countries like Sweden.

Yet airlines, which continue to be low in cash, have been reluctant to commit before they get a clearer sense on how the F.A.A. plans to transition to this new technology.

“Basically, it comes down to economics,” Mr. Mann said. “This is an industry that is not operationally driven. It is financially driven. And unfortunately, the airlines have learned to be very circumspect.”

Experts said the repeated delays in financing over the last few years have contributed to NextGen’s slow pace. The F.A.A. also has a history of being unable to complete large-scale investment programs on time and on budget.

In a report last month, the Department of Transportation’s inspector general said that another of the F.A.A.’s major technological programs, called En Route Automation Modernization, was four years behind schedule and could end up costing as much as $500 million more than its initial budget of $2.1 billion. The program, one of the building blocks of NextGen, is intended to track airliners at cruising altitude. It has suffered software glitches, including tagging flight numbers to the wrong planes, at its initial testing centers in Seattle and Salt Lake City.

“Yes, we have not been perfect in the past in technological rollouts,” said Michael P. Huerta, the F.A.A.’s deputy administrator. “But this one is different.”

Of NextGen, he added, “We are beyond this being a research and planning project and we are very much in implementations.”

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