LONDON (Reuters) - A computer system failure at British Airways on Saturday forced the airline to ground hundreds of flights, leaving 75,000 passengers stranded as its flight operations, call center and website all went down.
The British flag carrier has said the problem was caused by a power supply issue at one of its UK data centers. Below is what we know so far about the IT failure:
* BA described the problem as a "power supply issue at one of our UK data centers, which led to an exceptional power surge and caused physical damage to some of the infrastructure on one of our IT systems".
A spokeswoman said it was conducting an exhaustive investigation. "We're not going to engage in speculation at the moment," she added.
British Airways Chief Executive Alex Cruz said the power surge was so strong it rendered the back-up systems ineffective. BA have declined to give any further details about the cause of the surge or where the back-up systems are located.
* Scottish and Southern Electricity Networks (SEN), which manage the electricity distribution network in the area north of Heathrow where British Airways' headquarters are located, said its services were running as normal on Saturday morning.
"The power surge that BA are referring to could have taken place at the customer side of the meter. SEN wouldn't have visibility of that," a spokesman said.
When asked for details about what exactly happened, a BA spokeswoman did not elaborate on the statement above about an exceptional power surge.
* Cruz told BA's IT workers to focus on solving the problem rather than talking about it to the media.
"Guys, either you are part of the team working to fix this or you aren't," he said in a message to staff posted on the company's internal website. "We are not in the mode of 'debriefing on what happened' but rather 'let's fix this mode'."
He asked IT staff to report to London's Heathrow or Gatwick airports to help if they could.
* Ryanair, one of BA's low-cost rivals, said it kept its IT systems in three different locations to prevent any outage shutting down its operations.
"We have three IT locations in different countries across Europe, so if anything does happen, the second one kicks in and the third one will kick in," Chief Marketing Officer Kenny Jacobs told reporters as the group reported financial results.
"That's what most businesses would do. That's our approach and we've never had a major outage."
* The GMB Union said the computer failure stemmed from a 2016 decision to make a number of staff redundant and outsource the work to India in 2016.
BA's Cruz rejected the accusation, telling Sky News that the problem stemmed from "local issues around a local data center, which has been managed and fixed by local resources."
The company told a capital markets day in November 2016 that it had reduced its IT suppliers from 20 to four. "From an IT point of view, we go straight to offshore," Bill Francis, head of group IT said.
* Gil Hecht, the CEO of Israel-based IT outage prevention firm Continuity Software, said airline IT was "amazingly complex", but carriers would typically deploy layers of protection, with duplicates of every component and server.
The challenge was keeping the entire system correctly configured.
"Power supply cannot possibly bring down the entire thing, unless something was misconfigured in the first place," he said.
"It's very difficult to make sure that every time you configure something in the main system, that you also have updated the secondary systems.
"And if you're not 100 percent accurate, then when the main system fails, you can have a huge disaster."
Reporting by Alistair Smout, Paul Sandle, Karolin Schaps and Kate Holton; Writing by Guy Faulconbridge