WASHINGTON Ten years after Congress gave the go-ahead to modernize the nation's air traffic control system, one of the government's most ambitious and complex technology programs is in trouble.
The Next Generation Air Transportation System, or NextGen, was promoted as a way to accommodate an anticipated surge in air travel, reduce fuel consumption and improve safety and efficiency.
By shifting from radar-based navigation and radio communications technologies rooted in the first half of the 20th century to satellite-based navigation and digital communications, it would handle three times as many planes with half as many air traffic controllers by 2025, the Federal Aviation Administration promised.
Planes would fly directly to their destinations using GPS technology instead of following indirect routes to stay within the range of ground stations.
They would continually broadcast their exact positions, not only to air traffic controllers, but to other similarly equipped aircraft.
For the first time, pilots would be able to see on cockpit displays where they were in relation to other planes.
That would enable planes to safely fly closer together, and even shift some of the responsibility for maintaining a safe separation of planes from controllers to pilots.
But almost nothing has happened as FAA officials anticipated.
Increasing capacity is no longer as urgent as it once seemed.
The 1 billion passengers a year the FAA predicted by 2014 has now been shoved back to 2027.
Air traffic operations takeoffs, landings and other procedures are down 26 percent from their peak in 2000, although chronic congestion at some large airports can slow flights across the country.
Difficulties have cropped up at almost every turn, from new landing procedures that were impossible for some planes to fly to aircraft-tracking software that misidentified planes.
Key initiatives are experiencing delays and are at risk of cost overruns. And the agency still lacks "an executable plan" for bringing NextGen fully online, according to a government watchdog.
"In the early stages, the message seemed to be that NextGen implementation was going to be pretty easy: You're going to flip a switch, you're going to get NextGen, we're going to get capacity gains," said Christopher Oswald, vice president for safety and regulatory affairs at Airports Council International-North America.
"It wasn't realistically presented."
Some airline officials, frustrated that they haven't seen promised money-saving benefits, say they want better results before they spend more to equip planes to use NextGen, a step vital to its success.
Lawmakers, too, are frustrated. NextGen has enjoyed broad bipartisan support in Congress, but with the government facing another round of automatic spending cuts, supporters fear the program will be increasingly starved for money.
"It's hard not to be worried about NextGen funding ... because it's a future system," said Marion Blakey, who was the head of the FAA when the program was authorized by Congress in 2003 and now leads a trade association that includes NextGen contractors.
"There is a temptation to say the priority is keeping the existing systems humming and we'll just postpone NextGen."
In September, a government-industry advisory committee recommended that, given the likelihood of budget cuts, the FAA should concentrate on just 11 NextGen initiatives that are ready or nearly ready to come online.
It said the rest of the 150 initiatives that fall under NextGen can wait.
"You can't have an infrastructure project that is the equivalent of what the (interstate) highway program was back in the '50s and the '60s and take this ad hoc, hodgepodge approach to moving this thing forward," said Air Line Pilots Association First Vice President Sean Cassidy, who helped draft the recommendations.
The threat of funding cuts comes just as NextGen is nearing a tipping point where economic and other benefits should start to multiply if only the FAA and industry would persevere, said Alaska Airlines Chairman Bill Ayers, a supporter.
Responding to industry complaints, the FAA has zeroed in on an element of NextGen that promises near-term benefits: new procedures that save time and fuel in landings while decreasing greenhouse gas emissions.
Planes equipped with highly calibrated GPS navigation are able fly precise, continuous descents on low power all the way to the runway rather than the customary and time-consuming stair-step approaches in which pilots repeatedly decrease power to descend and then increase power to level off.