New Delhi, Nov 29 (PTI) IndiGo, Air India and Air India Express on Saturday started carrying out software upgrade of A320 family planes to address a potential flight control issue, and requisite modifications have been done for the majority of the 338 affected aircraft, an exercise that also resulted in delays of hundreds of flights.

Sources said airlines have not made any cancellations due to the system modification, but there have been flight delays of 60-90 minutes at various airports.

On Friday, Airbus said intense solar radiation could corrupt data critical to flight controls in a significant number of A320 family aircraft, and that the software changes required to fix the issue would cause operational disruptions.

As many as 338 A320 family aircraft operated by Indian airlines require the software upgrade to address a potential issue related to flight controls, and modifications have been carried out in more than half of the affected fleet, according to DGCA data.

The software upgrades have been completed for 189 A320 family planes out of the total 338 aircraft, as per the data available with the Directorate General of Civil Aviation (DGCA) till 10 am on November 29.

Software upgrades on all affected planes are to be completed by 5:29 am on November 30.

A total of 200 IndiGo planes have been affected, and software upgrades have been completed for 143 of them, while in the case of Air India, 113 aircraft have been impacted and upgrades have been done for 42 of them, the DGCA data showed.

In the case of Air India Express, 25 planes have been impacted, and software upgrades have been completed for four aircraft as of 10 am, according to data.

The software upgrades are being undertaken at the airlines' bases in Delhi, Bengaluru, Mumbai, Chennai, Hyderabad, Ahmedabad, and Kolkata.

DGCA on Saturday issued an Airworthiness Directive to airlines asking Indian operators to carry out the requisite software upgrades immediately.

This followed Airbus issuing an alert to operators globally and the European Aviation Safety Authority (EASA) coming out with an Emergency Airworthiness Directive regarding the potential issue.

On Friday, EASA said Airbus asked airline operators to install a serviceable Elevator Aileron Computer (ELAC) in the impacted aircraft. ELAC is for flight controls.

IndiGo, which operates over 2,300 flights daily, said that no flights have been cancelled as a result of the checks carried out on A320 family planes, but a few flights may experience minimal delays.

There have been no cancellations due to the task, and there is no major impact on schedule integrity across its network. However, some flights may be slightly delayed or rescheduled, Air India said in the morning.

Most of the nearly 6,000 affected aircraft worldwide need software upgrades, while some might require hardware realignment.

There are over 8,100 A320 family planes in service worldwide. These include A319s, A320 ceos and neos, and A321 ceos and neos, data from aviation analytics company Cirium showed.

Former pilot Ehsan Khalid told PTI Videos that ELACs are the brain and nervous system of the aircraft, and the software problem with one of the ELACs is significant.

When the pilot moves the control forward, it will cause the aircraft to pitch down and when it is moved backwards, the plane pitches down. This particular movement is done by pilot control, and if that happens on its own, then there is a problem, he said.

On October 30, he said a JetBlue aircraft experienced an uncommanded pitch down for seven seconds, which caused the aircraft to lose 100 feet and injured more than 15 people.

"At 35,000 feet, neither a loss of 100 feet nor seven seconds is critical. But if you remember the Ahmedabad crash, it happened during take-off, and seven seconds would have been enough to cause a catastrophic end. So humanity has been lucky this time.

"The aircraft manufacturer has openly acknowledged a software problem and has said it will fix it," Khalid said.

IndiGo, in a statement, said software upgrades have been done for 160 of the impacted 200 A320 family planes.

"We are pleased to confirm that the required actions have already been completed on 160 aircraft by 12:00 IST, and inspections on the remaining aircraft are progressing well and will be completed within the timeline," the airline said.

The airline said the required actions have already been completed on 160 aircraft by 12:00 IST, and inspections on the remaining aircraft are progressing well and will be completed within the timeline.

"We have already completed the reset on over 40 per cent of our aircraft that are impacted by this, and are confident of covering the entire fleet within the timeline prescribed by EASA," Air India said in a post on X in the morning.

On Friday, Airbus said an analysis of a recent event involving an A320 family aircraft has revealed that intense solar radiation may corrupt data critical to the functioning of flight controls.

"Airbus has consequently identified a significant number of A320 Family aircraft currently in service which may be impacted," it had said in a release.

Airbus had said it acknowledges these recommendations will lead to operational disruptions to passengers and customers. PTI RAM DRR