A U-2 spy plane may have triggered a computer problem at an air traffic control center that disrupted flights last week across the southwestern United States, US media reported Monday.

The Cold War-era plane, which is still part of the US fleet, somehow overloaded a computer system that displays data for air traffic controllers in the Los Angeles area, after its flight plan was incorrectly translated into computer code, NBC News and the Wall Street Journal said.

The glitch sparked a chain reaction and led the Federal Aviation Administration to halt flights into airspace Wednesday managed by the Palmdale air control center. The country-wide "ground stop" lasted for about an hour and affected hundreds of flights and thousands of passengers.

At Los Angeles International Airport, one of the country's busiest airports, there were 27 cancellations of arriving flights, as well as numerous delays and diversions to other airports. Flights also were delayed at several other airports in southern California.

A Pentagon spokesman, Colonel Steven Warren, said Monday: "I can tell you that there was a U-2 operating in this area in accordance with all FAA regulations.

"The U-2 filed all the prepared flight plan paper work and was conducting its operations in accordance with those filings."

The Federal Aviation Administration was investigating the incident, he said.

The computer problem raised fresh questions about the reliability of an expensive, new air traffic control network, known as ERAM, or En Route Automation Modernization. The system has already suffered budget setbacks and technical problems.

In last week's incident, both the primary and back-up systems were affected.