Bit flips: How cosmic rays grounded a fleet of aircraft

Radiation from space that led to more than 6,000 Airbus aircraft needing emergency computer updates could become a growing problem as ever more microchips run our lives.

"We need medical equipment," the pilot of a JetBlue passenger jet announced over the radio to air traffic control. His plane, an Airbus A320 commercial airliner had suddenly and unexpectedly dropped altitude during a flight from Cancun, in Mexico, to Newark, in New Jersey, US, on 30 October 2025. Three people appeared to have suffered "a laceration in the head", the pilot said. At least 15 people were later taken to hospital when the flight landed after being diverted to Florida.

A month later, this incident would lead to the mass grounding of more than 6,000 aircraft – one of the largest ever aviation industry recalls. It triggered widespread disruption and cancellations over the final weekend of November 2025, one of the busiest of the year for air travel following Thanksgiving in the US.

What caused all this? Tiny, high-energy particles from outer space, according to Airbus.

An initial investigation by the company revealed that the sudden drop in altitude was linked to a malfunction in one of the aircraft's computers that controls moving parts on the aircraft's wings and tail. The malfunction seems to have been triggered by cosmic radiation bombarding the Earth on the day of the flight.

According to emergency airworthiness directives issued by both the European Union Aviation Safety Agency (EASA) and the US Federal Aviation Authority (FAA), such radiation-triggered computer errors could, in the worst-case scenario, lead to an "uncommanded" change in altitude so severe that it might exceed "the aircraft's structural capability". They stated that urgent updates to the on-board computers were required in dozens of variants of Airbus A320, A319 and A321 aircraft before they would be allowed to carry passengers.

All those planes required software updates and, in some 900 cases, new computer hardware, to better protect them against the threat of space radiation wreaking havoc with their electronics.

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What Airbus says occurred on that JetBlue flight from Cancun to New Jersey was a phenomenon called a single-event upset, or bit flip. As the BBC has previously reported, these computer errors occur when high-speed subatomic particles from outer space, such as protons, smash into atoms in our planet's atmosphere. This can cause a cascade of particles to rain down through our atmosphere, like throwing marbles across a table. In rare cases, those fast-moving neutrons can strike computer electronics and disrupt tiny bits of data stored in the computer's memory, switching that bit – often represented as a 0 or 1 – from one state to another.

"That can cause your electronics to behave in ways you weren't expecting," says Matthew Owens, professor of space physics at the University of Reading in the UK. Satellites are particularly affected by this phenomenon, he says. "For space hardware we see this quite frequently."

This is because the neutron flux – a measure of neutron radiation – rises the higher up in the atmosphere you go, increasing the chance of a strike hitting sensitive parts of the computer equipment on board. Aircraft are more vulnerable to this problem than computer equipment on the ground, although bit flips do occur at ground level, too. The increasing reliance of computers in fly-by-wire systems in aircraft, which use electronics rather than mechanical systems to control the plane in the air, also mean the risk posed by bit flips when they do occur is higher.

The JetBlue incident is reminiscent of a case in 2008 involving an Airbus A330, when a Qantas flight fell hundreds of feet twice within 10 minutes, injuring dozens of passengers. A report by the Australian Transport Safety Bureau that followed could not conclude that a cosmic bit flip was definitely the cause – but it was left as the most likely scenario after several others were more or less ruled out.

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Airbus told the BBC that it tested multiple scenarios when attempting to determine what happened to the 30 October 2025 JetBlue flight. In this case also, the company ruled out various possibilities except that of a bit flip. It is hard to attribute the incident to this for sure, however, because careering neutrons leave no trace of their activity behind, says Owens.

An Airbus spokesman stressed "there is no link" between the JetBlue flight and the 2008 Qantas incident. The corrupted electronics on the Qantas flight were situated in a component that tracks and processes flight data. By comparison, the computer error that caused problems for the JetBlue flight occurred in the A320's Elac system, which controls certain moving parts of an aircraft's wings and tail to adjust elevation and roll.

Airbus's initial statement about the recall, however, has left some space weather scientists scratching their heads. The company referred to "intense solar radiation" on 30 October as potentially corrupting flight control data. But it wasn't a very notable day in terms of particles from the Sun washing over our planet. (Read more about how solar flares spill out across our Solar System.)

"On that particular day […], there wasn't anything special going on in terms of solar radiation," says Keith Ryden, professor of space engineering at the University of Surrey in the UK. "That's a little bit of a mystery from my point of view."

Owens is similarly perplexed. "The timing and location wouldn't immediately strike me as a solar event."

Subatomic particles that may trigger bit flips can originate in huge solar flares ejected by our Sun but they also arrive continually from sources outside our Solar System many light years away, and even from beyond our home galaxy, the Milky Way. These galactic cosmic rays are generated by huge stellar explosions known as supernovae and black holes. Airbus did not clarify why it referred to intense solar radiation, specifically, in responses to BBC questions.

There was, however, an unrelated major solar flare on 11 November – weeks after the JetBlue incident – where sensors mounted on UK weather balloons at 40,000ft (12km) measured one of the largest radiation events to hit Earth in roughly two decades. Some UK aircraft fitted with special instruments designed to monitor for fast-moving neutrons also registered the event.

"[Radiation levels] went up by a factor of 10 for a short period," says Ryden. While this is an indication that the Sun has recently experienced a period of high activity, it happened nearly two weeks after the JetBlue flight that led to Airbus's recall.

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In any case, the software updates rolled out by the company appear to be quick and easy to install. Many airlines completed them within hours. The software works by inducing "rapid refreshing of the corrupted parameter so it has no time to have effect on the flight controls", Airbus says. This is, in essence, a way of continually sanitising computer data on these aircraft to try and ensure that any errors don't end up actually impacting a flight.

By the morning of Monday 1 December, Airbus said the majority of its affected aircraft had received the necessary software updates and fewer than 100 planes were still to undergo modifications. Airlines reported that their services were largely returning to normal but that some disruption may continue in the following days.

More decisive action might be required to prevent such incidents in the future, though.

More like this:

• How solar flares spill out across the Solar System

• The superstorms from space that could end modern life

• The dream of beaming solar energy from orbit

Ryden and his colleagues have been working to help develop standards for hardening aircraft electronics against space radiation. He notes, however, that such standards "are not compulsory" in the aviation industry.

In the meantime, scientists are increasingly monitoring space weather and neutron flux to better understand the potential impact on digital technology. As computer chips have become smaller, they have also become more vulnerable to bit flips because the energy required to corrupt tiny packets of data has got lower over time. Plus, more and more microchips are being loaded into products and vehicles, potentially increasing the chance that a bit flip could cause havoc.

If nothing else, the JetBlue incident will focus minds across many industries on the risk posed to our modern, microchip-dependent lives from cosmic radiation that originates far beyond our planet.

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