European safety regulators have issued an emergency directive after flight-control data on Airbus A320-family jets was found to be vulnerable to high levels of solar radiation.

Airbus says the determination follows analysis of a recent event involving the single-aisle type.

While Airbus has not detailed the occurrence, FlightGlobal understands that it relates to a 30 October incident involving a JetBlue Airways A320 which experienced an “uncontrolled descent” for around 4-5s during a flight from Cancun to Newark, according to French investigation authority BEA.

BEA says the autopilot corrected the trajectory. It indicates the event was linked to the elevator aileron computer.

Airbus states that its analysis of the situation revealed that “intense” solar radiation “may corrupt data critical to the functioning of flight controls”.

It adds that a “significant number” of in-service A320-family jets could be affected.

FlightGlobal has learned that some 6,000 aircraft across the A320 and A320neo family could require modification, although this can be accomplished relatively quickly on 85% of them by reverting to a previous software version for the elevator aileron computer. Others could require hardware updates.

“Airbus has worked proactively with the aviation authorities to request immediate precautionary action from operators,” the airframer states.

It says operators are being alerted regarding the need to implement software or hardware protection to “ensure the fleet is safe to fly”.

These measures feature in an emergency airworthiness directive from the European Union Aviation Safety Agency, which states that a “malfunction” of the elevator aileron computer – which handles pitch and roll control – is a “possible contributing factor” to the JetBlue incident.

“This condition, if not corrected, could lead in the worst-case scenario to an uncommanded elevator movement that may result in exceeding the aircraft’s structural capability,” says EASA.

Airbus acknowledges that the directive will lead to operational disruptions for customers and airline passengers.

“We apologise for the inconvenience caused and will work closely with operators, while keeping safety as our number one and overriding priority,” it adds.