Much of the world’s fleet of about 11,000 Airbus A320 series aircraft – the most popular airliner in the world according to sales – are affected by a current emergency airworthiness directive from the European Union Aviation Safety Agency and the US Federal Aviation Administration requiring that operators modify their aircraft control software to make it more resistant to the effects of solar radiation.

This followed a sudden loss of height in the cruise involving a JetBlue A320 en route from Cancun, Mexico to Newark, USA on 30 October. Solar radiation is believed to have been responsible for corrupting the data in one of the aircraft’s flight control computers causing the sudden height loss – which injured several passengers. Recovery action by the pilots ensured the aircraft diverted safely to Tampa, Florida.

Most younger A320s need only a quick software patch to harden the microchip resistance in their flight control computers against particularly vigorous bursts of solar radiation, but nearly a thousand of the oldest aircraft may need to change the units.

Solar radiation is known to be able to interfere with GPS signals, radio communication, inertial navigation systems, autopilot, and full-authority digital engine controls (FADEC), although incidents are rare. A mysterious sudden pitch-down by a Qantas A330 in the cruise over Western Australia in October 2008 is now reckoned to have been caused by corrupted data from an air data inertial reference unit (ADIRU) that may have been subject to solar radiation damage.

All aircraft are more vulnerable than suface vehicles to solar radiation effects because, at high altitude, there is less atmospheric attenuation of the sun’s electromagnetic energy. Polar flights are particularly vulnerable because the earth’s magnetic field provides less shielding and the troposphere is at a lower altitude there.

A320 series aircraft have three three flight control primary computers (FCPC), two flight control secondary computers (FCSC), and a flight augmentation computer, all of which provide considerable systems redundancy, plus a cross-checking capability to detect and correct anomalous data.

The UK Civil Aviation Authority said today that there had been virtually no disruption to flight schedules because airlines were so quick to apply software fixes.

1 December 2025: a statement from Airbus on this date claimed that only about 100 A320 series aircraft remained to receive the softwear hardening required by EASA an the FAA.