Thousands of Airbus planes were grounded after it was discovered that intense solar radiation could interfere with onboard flight control computers, causing delays around the world.
Some 6,000 A320 aircraft are believed to be affected, half of the European firm’s global fleet, but it is understood that most will be able to fly again after undergoing a rapid software update.
The UK’s aviation regulator said there would be “some disruption and cancellations of flights”, although the impact on airports appears to be limited.
Airbus said it discovered the problem after an investigation into an incident in which a plane flying between the United States and Mexico suddenly lost altitude in October.
The JetBlue Airways flight made an emergency landing in Florida after at least 15 people were injured.
In addition to the A320, the company’s best-selling aircraft, the vulnerability also affects the A318, A319 and A321 models.
It is understood that on around 5,100 Airbus aircraft, the problem can be fixed by a relatively simple software update that would normally take around three hours.
However, the remaining 900 planes, which are older versions, will need their on-board computers physically replaced and will not be allowed to carry passengers again until the work has been completed.
How long it takes will depend on the availability of replacement computers.
Airbus said it recognized this will cause “operational disruptions for passengers and customers” and apologized.
Aviation analyst Sally Gethin told BBC News the situation is “very unusual”, and said the inconvenience to passengers will depend on the “different approaches” airlines take to updating their software.
“I understand that Lufthansa is saying it could take its planes out of service to do this, in other cases the airlines say it shouldn’t have much impact at all,” he said.
In the UK, disruption at airports has been limited so far. London’s Gatwick Airport reported “some disruption” while Heathrow said it had not experienced any cancellations.
The extent of the outage varies between airlines: British Airways is understood to not be greatly affected by the issue, while Wizz Air and Air India said they were already making updates.
Easyjet said it “expected this to cause some disruption” but later added that it had started and “already completed the software update on many aircraft” and was planning a full service on Saturday.
In the United States, the software problem arose on Thanksgiving Day weekend, one of the busiest tourist periods of the year.
American Airlines said 340 of its planes were affected and it expected “some operational delays,” but added that the vast majority of the upgrades would be completed by Friday or Saturday. Delta Airlines said it believed the impact on its operations would be “limited.”
In Australia, low-cost airline Jetstar canceled 90 flights after confirming that around a third of its fleet was affected.
Tim Johnson, policy director at the UK Civil Aviation Authority, said Airbus’ notice “unfortunately may mean that there will be some disruption, some delays or cancellations in the coming days.”
He added that aviation remains “one of the safest forms of transportation” due to the rigorous maintenance programs implemented by airlines, and described the mass suspension of flights as “a very rare event.”
Transport Secretary Heidi Alexander said “the impact on UK airlines appears limited” and added: “It is encouraging that this issue has been identified and addressed so quickly, demonstrating the high standards of aviation safety globally.”
The problem identified with the A320 aircraft relates to computer software that calculates the elevation of an aircraft.
Airbus discovered that at high altitudes its data could be altered by the intense radiation periodically released by the sun.
That led to the October incident in which a plane suddenly lost altitude, although the manufacturer said it was the only time such an incident had occurred.
The European Union Aviation Safety Agency (EASA) has issued an emergency airworthiness directive, ordering that the problem be fixed before each plane can carry passengers again.
They will be allowed to make so-called “ferry flights”, without passengers, to reach a maintenance facility.
The A320 family are the so-called “fly by wire” aircraft. This means that there is no direct mechanical link between the cockpit controls and the parts of the plane that actually govern flight, but rather the pilot’s actions are processed by a computer.
