A new computer system key to modernization of the nation's air traffic control system has run into problems, raising doubts about whether it can be operational 15 months from now when current computers must be replaced, union officials said Wednesday.

The Federal Aviation Administration tried unsuccessfully to deploy the new computer system last weekend at a regional air traffic control center in Salt Lake City, the first of 20 regional facilities where the computers need to go into operation before the end of 2010.

That's when FAA's contract with IBM to maintain the present computer system expires. The present system used by controllers to guide air traffic relies on a unique computer language called Jovial that's understood by a dwindling number of technicians.

"They are racing the clock here. They have to get this to work failure is not an option," said Doug Church, a spokesman for the National Air Traffic Controllers Association.

The computer system is an important part of FAA's plan to switch from an airspace system that tracks aircraft using World War II-era radar technology to one based on satellite technology. Full deployment of the GPS-based system is expected between 2015 and 2020 at a combined cost to the government and the airline industry of about $35 billion.

The switch from the old computer system to the new system was made at the Salt Lake center about 11:30 p.m. MDT Friday. The new system was shut down about nine hours later after it misidentified an airliner, controllers said.