Dozens of airlines from Asia to the United States said they had carried out a snap software retrofit ordered by Airbus, and mandated by global regulators, after a vulnerability to solar flares emerged in a recent mid-air incident on a JetBlue A320.

Airbus shares suffered their sharpest single-session fall in over a year after a report about an issue on several of its planes. Reuters, citing industry sources, reported an industrial quality issue affecting fuselage panels of several dozen aircraft in the A320 family.

Airbus has almost returned all A320 jets to service after implementing urgent software fixes due to a solar radiation vulnerability. Under 100 remain grounded.

One of the world’s largest airplane makers said Friday that intense solar radiation may corrupt data critical to flight controls on a “significant number” of its most popular aircraft, prompting a swift response from several airlines. Airbus attributed the revelation to a recent analysis involving its A320 family of aircraft.

It was a hectic weekend with dozens of flights cancelled and thousands of passengers affected. But behind the scenes, engineers at the country’s airlines were able to resolve the Airbus A320 software issues in less than 48 hours.