Swanwick air traffic control centre 'plagued by problems'
Thousands of flights have been delayed due to problems at a key air traffic control centre in Swanwick, in Hampshire, but it is not the first time that the state-of-the-art facility has hit the headlines.
Swanwick controls aircraft in the 200,000 square miles of airspace above England and Wales, and was built to enable controllers to look after more planes and effectively expand UK airspace.
But since it opened 11 years ago, the £623m London Air Traffic Control Centre - which employs around 1,300 controllers - has experienced a number of technical difficulties, from computer glitches to faulty equipment.
The facility, which handles 5,000 flights every 24 hours, was delayed even before it opened, eventually taking over operations in January 2002 - six years after its planned commissioning date.
National Air Traffic Services (Nats) - the partially-privatised company that provides air traffic control to commercial flights in the UK's airspace - said the delay in its opening was due to problems with the software used to power its systems.
The software was based on a package being developed by the US air traffic control network as part of a huge upgrade.
But the American project collapsed, leaving Nats and its software developers to pick up the pieces and raising the cost of the centre by nearly £150m on top of the original £475m.
In 2008, Richard Wright of Nats told the BBC Swanwick had had a "difficult birth", and that improving the software took "much longer than planned", but he said that it had been operating since 2002 "without a single serious safety incident".
But while the centre has generally been working well, it hit the headlines shortly after opening - and again in 2008 - for problems with its computer systems.
And in July this year, flights in southern England were delayed due to "technical problems".
There have also been issues with equipment. Almost a year after it first opened, a senior air traffic controller told BBC Radio 4's Today programme that some of the difficulties at Swanwick were "potentially catastrophic".
The controller, who did not want to be named, detailed health and safety concerns and complications with radio communications - which he said cut out erratically.
But Richard Everitt, the then chief executive of National Air Traffic Control Services, said that the service had "exceeded safety targets" that year.
Nats has said the latest delays were caused by a problem with the internal telephone system, which was having "difficulty switching from night time to daytime operation".
It said that the centre was unable to open additional control positions to cope with the demand in traffic.
Nats - which took responsibility for the centre in 2001 - has been operating since 1962 and last year handled 2.1 million flights, carrying some 220 million passengers in the UK.
In the 2012 and 2013 financial year, delays to flights which were attributable to Nats averaged just 1.4 seconds.