As the weekend approached, airlines globally faced a wave of flight cancellations and delays. This disruption arose from the need to update software on a popular commercial aircraft model, following findings that suggested a computer code issue might have led to a JetBlue plane’s unexpected altitude drop last month.

Airbus announced on Friday that their investigation into the JetBlue incident uncovered that high levels of solar radiation could potentially alter data crucial for the operation of flight controls in their A320 aircraft series.

In response, the Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency mandated airlines to implement a new software patch to rectify the problem. This directive will affect over 500 aircraft registered in the United States.

The European safety body warned that this software fix could result in “short-term disruption” to flight schedules. The issue reportedly stemmed from a recent update to the onboard computer systems of the aircraft.

In Japan, All Nippon Airways, which manages a fleet of over 30 of these aircraft, had to cancel 65 domestic flights scheduled for Saturday. The airline indicated that more cancellations could occur on Sunday.

This software update comes at a critical time as U.S. travelers begin returning from the Thanksgiving holiday, which marks the busiest travel period in the country.

American Airlines has about 480 planes from the A320 family, of which 209 are affected. The fix should take about two hours for many aircraft and updates should be completed for the overwhelming majority on Friday, the airline said. A handful will be finished Saturday.

American expected some delays but it said it was focused on limiting cancellations. It said safety would be its overriding priority.

Air India said via the social platform X that its engineers were working on the fix and completed the reset on more 40% of aircraft that need it. There were no cancellations, it said.

Delta said it expected the issue to affect less than 50 of its A321neo aircraft. United said six planes in its fleet are affected and it expects minor disruptions to a few flights. Hawaiian Airlines said it was unaffected.

Mike Stengel, a partner with the aerospace industry management consulting firm AeroDynamic Advisory, said the fix could be addressed between flights or on overnight plane checks.

“Definitely not ideal for this to be happening on a very ubiquitous aircraft on a busy holiday weekend,” Stengel said from Ann Arbor, Michigan. “Although again the silver lining being that it only should take a few hours to update the software.”

At least 15 JetBlue passengers were injured and taken to the hospital after the Oct. 30 incident on board the flight from Cancun, Mexico, to Newark, New Jersey. The plane was diverted to Tampa, Florida.

Airbus, which is registered in the Netherlands but has its main headquarters in France, is one of the world’s biggest airplane manufacturers, alongside Boeing.

The A320 is the primary competitor to Boeing’s 737, Stengel said. Airbus updated its engine in the mid-2010s, and planes in this category are called A320neo, he said.

The A320 is the world’s bestselling single-aisle aircraft family, according to Airbus’ website.

Associated Press writers Mari Yamaguchi in Tokyo and Jennifer Kelleher in Honolulu contributed.