Swanwick air traffic control centre in Hampshire has suffered a computer failure, leading to delays at airports in London, the south-east and further afield.
The £623m air traffic control centre is one of the busiest and most complex in the world - but has not been without problems.
January 2002: The centre opens - six years overdue.
It controls 200,000 sq miles of air space, from an operation room covering 2,000 sq metres.
Its computer system was tested for 650,000 hours before launch, and has more than two million lines of software code - one of the most sophisticated IT projects in the country.
March and April 2002: A problem at West Drayton control centre had a knock-on effect at Swanwick, where controllers were forced to sit in front of their expensive computer screens keeping note of aircraft with pen and paper.
At the time National Air Traffic Services (Nats) stressed it was not Swanwick's own systems that were at fault, but a separate computer and data-link.
17 May 2002: After a regular monthly computer upgrade at Swanwick it was discovered that only half the computer terminals were working at full capacity. Air traffic controllers had to halve the number of aircraft normally in the skies.
Nats insisted safety had not been compromised, but lengthy delays and cancellations left airlines and passengers annoyed.
May 2002: An air traffic controller sent a Glasgow plane to Cardiff after misreading small computer text at Swanwick, Computer Weekly reported.
According to confidential documents obtained by the magazine, the controller had difficulty distinguishing the codes for the two cities.
Another also reportedly misread the heights of planes and sent an aircraft into the wrong airspace.
December 2002: A senior air traffic controller with some 40 years experience behind him told the BBC that radio communications were cutting out erratically, with the potential to cause drastic problems.
But the head of the air traffic control service insisted the service was safe.
25 September 2008: A computer fault leads to delays at airports, including Heathrow, Luton, Stansted, and Belfast.
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