The airspace over London was briefly closed Friday afternoon due to what authorities said was a computer failure at one of Britain's two air traffic control centres.
The 35-minute shutdown caused flight delays in and out of London and flight slowdowns in other parts of Europe that officials said would linger into Saturday.
Disruption on this scale is simply unacceptable and I have asked NATS for a full explanation of this evening's incident.
NATS, Britain's national air traffic service, said it suffered a technical problem at its air traffic control centre in Swanwick, southern England.
The shutdown came at a busy time at the start of the weekend in a sprawling city with five commercial airports, including London Heathrow, Europe's busiest, as well as Gatwick, Luton, Stansted and London City Airports.
British Transport Secretary Patrick McLoughlin said he had asked for a full explanation for Friday's "simply unacceptable" aviation disruption.
"Any disruption to our aviation system is a matter of the utmost concern, especially at this time of year in the run up to the holiday season," he said in a statement.
"Disruption on this scale is simply unacceptable and I have asked NATS for a full explanation of this evening's incident. "I also want to know what steps will be taken to prevent this happening again," he added.
Plagued by problems
Airline security analyst Chris Yates told the AP news agency that such computer issues happen rarely. One that occurred about two and a half years ago resulted in disruptions that lasted for days.
The Swanwick centre has been plagued by problems since it opened more than a decade ago. It only swung into operation in 2002, six years after its planned commissioning date and double its original budget.
Software and reliability issues have caused repeated disruption since.
Heathrow is one of the world's busiest international airport. Over 67 million passengers travel through it annually on services offered by 90 airlines travelling to over 180 destinations in over 90 countries, according to its website.