Airlines around the world canceled hundreds of flights and rushed to rearrange their itineraries as a serious software bug threatened to disrupt the Christmas holiday season.

More than 6,000 aircraft, more than 50% of the global fleet, could be affected by the required fix, manufacturer Airbus said late Friday. A directive from the European Aviation Safety Agency requires the software update to be carried out before the next flight of the aircraft in question.

Airlines rushed to implement the updates on their A320 fleet, disrupting the travel plans of thousands of passengers. This is a rare technical problem on the Airbus aircraft. The A320 is the best-selling commercial aircraft in history, meaning any disruption directly affects air travel from New Zealand and India to Latin America.

The emergency software fix directive came after a recent incident in which a JetBlue aircraft malfunctioned when intense solar radiation corrupted data critical to the operation of flight control systems. Depending on the age of the aircraft, the update could be done digitally (downloaded) or require a complex and time-consuming hardware change.

Airbus recognizes that these guidelines will lead to disruption for customers and travelers, the company said.

The update process

Aircraft that need the update must be rolled back to a previous version of the software. This process can take as little as 2 to 3 hours. However, about 1,000 older aircraft will need a hardware upgrade and will remain grounded for a longer period, according to reports.

Airplanes that had not received the latest version of the software, which is at risk of being corrupted by solar radiation, are not affected.

Airbus' CEO said the company's teams are working around the clock to support operators and ensure updates are installed as quickly as possible to get aircraft back in the air.

The revelation was a major blow to Airbus, as the A320 jets have been the backbone of global aviation for decades. The sudden need for a software fix has also caused disruption for airlines that rely solely on Airbus' fleet.

The image in America and Asia

In the US, airlines operating about 1,600 A320 aircraft have tried to proceed with the repair with minimal disruption. The US Civil Aviation Authority said its own directive affects 545 A320 aircraft.

American Airlines said that of its 209 affected aircraft, fewer than 150 required updates by Friday evening. IndiGo said that of its 200 aircraft requiring an inspection, 160 had already completed the procedures by Saturday afternoon, with no cancellations.

Colombia's Avianca announced that more than 70% of its fleet is affected and temporarily suspended ticket sales until December 8. ANA in Japan canceled 95 flights on Saturday, causing disruption for about 13,200 passengers.

Wizz Air announced that it had completed all required updates overnight and that its operations had returned to normal. Cancellations were reported in Australia and New Zealand, as Jetstar and Air New Zealand grounded aircraft for the updates.

Britain's Civil Aviation Authority said that most of the updates have already been installed and that the impact on passengers is minimal.

The A320 family competes with the Boeing 737, with both aircraft types being the mainstays of commercial aviation. Airbus has already come under pressure from problems with the A320neo's new Pratt & Whitney engines, which have led to additional groundings.

The A320 was introduced in the late 1980s, and its success made Airbus a global leader. The family includes the A319, A320 and A321, while the neo versions with new engines were launched a decade ago. The fix affects all versions, both the newer A320neo and the older classic.

What applies to Aegean and Sky Express

As for the two Greek airlines,  Aegean and Sky Express,  which have Airbus aircraft in their fleet,  state that there will be no problems and no changes to flights. 

Aegean  in its announcement states:

AEGEAN immediately completed the implementation of the Airbus directive – The company's flight schedule continues as normal

AEGEAN informs that, following the directive issued last night by Airbus for the immediate software rollback of certain A320 family aircraft, it promptly activated all required operational and technical procedures.

The implementation of the directive has already been successfully completed and the flight schedule continues normally, without any changes or variations.

The safety of our passengers and flight crews is our non-negotiable priority.

For its part, Sky Express announced: 

SKY express informs its passengers that the recent Airbus directive, which affects 6000 A320 family aircraft, has no impact on the company's fleet and flight schedule, as our aircraft are not included in the specific series requiring the upgrade. All SKY express flights are operating normally and operations continue uninterrupted.

The incident that prompted the major repair operation  involved a JetBlue Airways plane flying from Cancun, Mexico, to Newark Liberty International Airport in New Jersey on October 30. Flight 1230 made an emergency landing in Tampa, Florida. Several people were taken to the hospital as the Airbus A320 suddenly lost altitude after experiencing a flight control problem.

According to Airbus data, there are approximately 11,300 A320 aircraft in operation, of which 6,440 are of the basic A320 model.

According to the relevant directive issued by the European Union Aviation Safety Agency, from today, these aircraft will be allowed to carry passengers only after they have been repaired. Flights without passengers will be allowed in order to be transported to the designated facilities for their repair.