The cornerstone of the sweeping new system intended to transform global aviation is way behind schedule and over budget, causing airlines to doubt whether they should pony up their share of the cost, a House subcommittee was told Wednesday.

Software problems have put the multi-billion dollar En Route Automation Modernization (ERAM) program four years behind schedule and $330 million over budget, said Calvin L. Scovel III, inspector general for the Department of Transportation.

Scovel told the House aviation subcommittee that there have been “major concerns” from the aviation industry stakeholders about the pace of progress.

The new routing system that will allow air traffic controllers to handle vastly more airplanes is the first step and a vital component in the biggest aviation investment in U.S. history, the revolutionary Next Generation Air Transportation System (NextGen).

NextGen will replace the system that governs the path of aircraft from departure gate until the doors open at their destination, costing taxpayers as much as $27 billion and airlines $10 billion more.

With the volume of air traffic projected to almost double during the next two decades, NextGen would replace radar tracking with Global Positioning Satellites (GPS), allow more direct routing that would save time and fuel, and provide pilots and controllers with more precise data about the distance of one plane from another.

“We view NextGen as one of the most important infrastructure investments for our nation,” John D. Porcari, deputy secretary of transportation, told the House panel. “This is a system of systems, so it’s very complex implementation. This [also] is a U.S. technological leadership issue.”

If the Federal Aviation Administration finishes developing and implementing NextGen before a consortium of European nation’s create their own, that would vault the companies that produce the U.S. system into the forefront of the technological marketplace.

There was general agreement from those who testified, including representatives of the airline industry and the air traffic controllers union, that Congress and the White House had helped right a wobbly program in the past two years.

Rep. Jerry F. Costello (D-Ill.) credited Transportation Secretary Ray LaHood, former FAA administrator Randy Babbitt and acting FAA administrator Michael P. Huerta with bringing the airlines and controllers into a development process that for years had been a closed discussion between FAA engineers and equipment manufacturers.

Controllers’ union president Paul Rinaldi said his members have been instrumental in finding the bugs in the ERAM system.

After decades of hearings on what now is known as NextGen, some members of the House committee voiced frustration with the pace of progress.

Scovel, whose reports on NextGen have scalded the FAA, was asked whether the program ultimately would be worth the money.

“Come the promised land, when NextGen is in place, NextGen will be a good return on investment,” he said.