Although National Air Traffic Services (Nats), which owns the Swanwick centre, had built costly and elaborate resilience into the systems, it appears that there was no expectation that a single workstation could cause so many others to fail.
The problem began at about 6.30am on Friday when Nats tried to boot up about half of Swanwick's 200 IBM Unix-based workstations that had been switched off during the night. A single workstation which had had a routine software update installed blocked the booting up of the 100 workstations.
This forced Nats to operate at 50% of capacity. To allow controllers on the remaining 100 workstations to cope, some aircraft were instructed not to take off until the problem was circumvented and the systems were back to normal at about 11am.
The disruption was compounded by an unconnected failure of systems at the main European air traffic control hub, Eurocontrol in Brussels.
The systems crash at Swanwick and complaints about the lack of clarity of some display screens raise the question of whether the Civil Aviation Authority (CAA) should have certified the systems as safe to go live in January.
Swanwick controls about 5,000 flights a day over England and Wales from IBM RS/6000 workstations that run the AIX operating system. The Lockheed Martin software contains more than two million lines of code.
A spokesman for the CAA said his organisation is in no doubt that the Swanwick systems are safe. A Nats spokesman said the exact cause of the workstation's crash and why it affected so many systems is still being investigated.