A new high-altitude air traffic control system is taking longer than expected to bring on line and at higher costs than planned, a U.S. government watchdog said on Dec. 23.

The Federal Aviation Administration (FAA) has already spent US$1.8 billion on the system aimed at providing faster routes and safely packing more planes into the high-altitude cruising phase of flight.

Transportation Department Inspector General Calvin Scovel said it could take between three to six years and up to US$500 million more to finish the project managed by the FAA and its contractor Lockheed Martin Corp.

Significant problems with software designed for managing flight data led to radar-related failures, misapplication of flight data, and other issues at a test site in Salt Lake City, according to Scovel's report.

"To compensate for these problems, controllers were forced to rely on a large number of workarounds that increased workload and fatigue and diverted them from managing traffic," Scovel said in the report.

FAA said in a statement that controllers are using the system again and testing at other facilities is going well.

"We are confident that we will continue to meet (program) milestones and deadlines," the statement said. A new deployment schedule will be released in coming weeks.

Scovel said the glitch with the high altitude effort was one of several challenges faced by the FAA in laying the groundwork for adopting a satellite-based air traffic system to replace the aging network tied to radar.

Other problems or potential problems include training, an FAA culture that embraces big initiatives rather than smaller steps, and convincing airlines that long-delayed government-run modernization is on the right course.

Airlines will be required to outfit new planes with cutting edge navigation equipment at considerable cost. Only a few carriers have made even modest investments with industry pushing government to cover a substantial amount of new costs.

Proposals in Congress this year to move modernization forward fell short over questions on how to fund its multibillion-dollar price tag.

Key operational decisions for the high altitude hardware and software system were scheduled for December 2009. But FAA halted tests in March for a period to fix more than 200 problems and develop a new course of action.

Scovel warned the schedule could slip further as new glitches are identified and the system is tested at bigger centers. "Our work shows that considerable work and risk lie ahead."

The report was requested by incoming U.S. House of Representatives Transportation Committee Chairman John Mica and other leaders on the panel.