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Computer failure grounds United

Passengers wait inside the United Airlines terminal at O'Hare airport in Chicago yesterday. Passengers wait inside the United Airlines terminal at O'Hare airport in Chicago yesterday. (Frank Polich/Bloomberg News)

CHICAGO -- United Airlines, a unit of UAL Corp., yesterday said it was suffering "residual delays" hours after resolving a system wide, computer failure that grounded its flights around the world.

The number two U S airline said the problem has been resolved and that United was working to restore regular service. The airline had no specific information on delays.

A United spokesman said the computer failure lasted from 9 to 11 a.m. EDT .

The computer that failed measures the weight of an airplane before departure. As a result, United planes were unable to take off during the incident.

At Logan International Airport in Boston, United and other airlines faced scattered delays in the morning as firefighters and public-safety crews were scrambled for an emergency landing of an American Eagle jet from Toronto whose pilot was unable to land the plane safely on his first approach. But by yesterday evening, about a dozen incoming United flights were still reported being delayed 30 minutes or more, including an inbound flight from Tokyo via O'Hare International Airport in Chicago that was cancelled.

Low-fare competition and soaring fuel costs have battered the industry in recent years. Several airlines, including United, restructured in bankruptcy, cutting costs steeply.

Since restructuring, United and its rivals have put a high premium on service, hoping to attract new customers and spur brand loyalty. United has targeted business travelers in particular.

It is uncommon for massive delays to result from computer problems. A more common culprit is foul weather.

In February, low-cost carrier JetBlue Airways saw its reputation for good service tarnished after a weather-related snafu ground planes for days and stranded some passengers on aircraft for hours. Peter J. Howe of the Globe staff contributed to this report.