By Ingrid Melander and Tim Hepher
PARIS (Reuters) - Thousands of passengers were delayed worldwide after a computer glitch temporarily halted departures at United Airlines, the latest in a series of outages to affect rival companies in the industry.
United said on Twitter that an issue with its weight reporting system delayed flights starting Thursday, and it resolved the problem by 3 AM EDT (07:00 GMT) on Friday. The No.3 U.S. airline by passenger traffic is working to determine the cause, its spokesman said Friday.
Weight and balance systems calculate a plane's centre of gravity and if it is carrying no more than it can handle to fly.
On Friday, delays often lasted 10 to 20 minutes due to United's crew having to handle some tasks manually, the spokesman said. But some passengers reported they had to wait aboard planes or inside terminals for several hours.
"On the plane for more than an hour, away from the gate and no communication. What's happening?," one passenger tweeted.
In Paris, passengers complained as check-in lines grew for a flight to New York, a Reuters reporter said on Friday morning.
As of 5:00 PM EDT (21:00 GMT), United had cancelled 11 flights and delayed 216, or 9 percent of its operation, according to flight tracking website FlightAware.com.
The large size of global airlines and their need to automate systems to be reliable mean recovering from glitches will almost always take some time, despite investment and redundancies, said Bob Edwards, United's former chief information officer until 2014.
This is the third computer glitch recently to hit United's owner United Continental Holdings Inc (UAL.N) and the latest in a series of problems that have tested airlines' reliance on ageing technology.
This has prompted some experts to question whether the airline industry has invested enough in technology infrastructure, given new profits from baggage and cancellation fees.
On June 2, 2015 software needed to dispatch United's flight plan briefly lost functionality.
In July 2015, the same airline's flights were disrupted after a computer problem blocked access to reservations records.
This August, Delta Air Lines Inc (DAL.N) cancelled thousands of flights and delayed many others after a power outage hit its computer systems.
And in September, a system-wide computer problem at British Airways (ICAG.L) caused significant delays.
After the previous incidents, United said it had invested in backup plans.
(Reporting by Ingrid Melander, Tim Hepher; Additional reporting by Jeffrey Dastin in New York; Editing by Keith Weir, Nick Zieminski and Bernard Orr)