Airbus aircraft resumed normal operations on Monday after the manufacturer implemented urgent software modifications faster than anticipated, following a massive recall that affected its A320 fleet over the weekend.

Dozens of airlines reported completing an urgent software update mandated by Airbus and enforced by global regulators, after a potential vulnerability to solar flares was identified during a recent in-flight incident involving a JetBlue A320.

On Monday, Airbus stated that the vast majority of the approximately 6,000 A320 family aircraft affected by the safety alert had been modified, with fewer than 100 planes still requiring work.

"We are working with our airline customers to support the modification of the remaining fewer than 100 aircraft to ensure their return to service," Airbus said in a statement.

Sources familiar with the matter said the decision to recall about half of the A320 family fleet was made shortly after last week's incident on the JetBlue-operated flight.

As of 08:42 GMT, Airbus shares were down 2.53% at EUR199.28.

Following discussions with regulatory authorities, Airbus issued an eight-page alert to hundreds of operators on Friday, ordering the temporary grounding of aircraft and repairs before their next flight.

This directive was seen as Airbus's largest emergency recall to date and immediately raised concerns about travel disruptions, particularly during the busy Thanksgiving weekend in the United States.

IMPACT REVISED DOWNWARD

According to industry sources, the broad warning revealed that Airbus does not have real-time knowledge of the software version in use due to delays in information transmission.

While airlines initially struggled to assess the impact--since the alert did not specify affected aircraft serial numbers--engineers identified within 24 hours which planes required updates.

Several airlines have since revised downward their estimates of the number of aircraft involved and the time needed to complete the work, which Airbus initially estimated at three hours per plane.

The update involved reverting to a previous version of the software that manages the aircraft's nose angle. This process requires downloading the earlier version via a cable from a device known as a "data loader," which is brought into the cockpit to prevent cyberattacks.

EasyJet and Wizz Air said Monday they had completed the updates over the weekend without canceling any flights.

JetBlue planned to return 137 of the 150 affected planes to service by Monday, but noted that around 20 flights would still be canceled.

Questions remain regarding a subset of generally older A320 family aircraft that will require a new computer rather than a simple software reset. The number of affected planes has been reduced from initial estimates of 1,000, according to industry sources.

This is the first time since the crisis began that Airbus has faced such intense global scrutiny over safety issues. CEO Guillaume Faury has issued a public apology.

(Reporting by Tim Hepher, Allison Lampert, and David Shepardson; French version by Etienne Breban, edited by Blandine Hénault and Augustin Turpin)