The aircraft affected are from the A320 family - which are used by numerous airlines - and need a systems update before they can fly again.

Airbus issued the alert after analysis of a flight involving an A320 showed "intense solar radiation may corrupt data critical to the functioning of flight controls".

It is understood the incident that triggered the warning involved a JetBlue flight from Cancun, Mexico, to Newark on 30 October.

That flight was diverted to Tampa International Airport after it suffered a flight control issue and experienced a sharp loss of altitude, which injured at least 15 passengers.

An Airbus spokesperson told Sky News the software change would affect up to 6,000 planes.

The fix involves A320 aircraft reverting to an earlier software version and Airbus stressed it would only take two to three hours for most planes.

However, it said some jets would also need new hardware and therefore would be affected for longer. Industry sources estimated about 1,000 aircraft could be in this position.

America's aviation watchdog has issued an emergency order to immediately replace or modify the software, mirroring one from the European Union Aviation Safety Agency.

'Very concerning'

Gatwick said a "small number" of carriers based there were affected, but warned disruption was still possible. It urged passengers to contact their airline.

Heathrow said it wasn't expecting any disruption.

"The good news is it seems the impact on UK airlines seems limited, with a smaller number of aircraft requiring more complex software and hardware changes," said Transport Secretary Heidi Alexander.

She said it was "heartening this issue has been identified and will be addressed so swiftly".

Airbus is understood to have traced the issue to the ELAC (Elevator and Aileron Computer) system, which sends commands to elevators on the plane's tail. These in turn control the aircraft's pitch or nose angle.

Travel expert Simon Calder said the situation was "very concerning" but stressed "aviation remains extraordinarily safe".

He warned customers might not be entitled to compensation if they're delayed as the issue would be considered out of airlines' control.

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What have airlines said?

EasyJet said it had already completed the software update on many aircraft and was working closely with safety authorities.

"We plan to operate our flying programme normally on Saturday and ask that customers travelling continue to monitor their flights on flight tracker," it added.

The airline said passengers would be informed of any changes by email, SMS, or the flight tracker

British Airways said it wasn't expecting any problems and that only three of its planes were affected.

For American Airlines - the world's largest operator of the A320 - the issue was more significant, with 209 aircraft needing an update.

It comes on a huge travel weekend stateside as many travel home after Thanksgiving. However, the US carrier said the fix would be completed for the vast majority of its planes on Friday.

Others affected include Japan's All Nippon Airways, which cancelled 65 domestic flights on Saturday, and Air France - which said it was cancelling 35 flights.

Ireland's Aer Lingus said a limited number of aircraft were impacted, while Wizz Air has started the software update but said some weekend flights could still be affected.

"Passengers who booked directly with Wizz Air via the website or mobile app will be notified of any schedule changes," the airline said.

The aircraft manufacturer is carrying out software updates for 6,000 of its jets - around half the global fleet - threatening travel disruption for airline passengers.

The UK's Civil Aviation Authority said it expects some disruptions to airlines and flights, with easyJet and Wizz Air saying they will take some planes briefly out of service to do the repairs.

But why have airlines been told to carry out a software update for the planes, and how is solar radiation involved?

Follow the latest updates on this story

What triggered the repair order?

It is understood the incident that triggered the unexpected repair order involved a JetBlue flight from Cancun, Mexico, to Newark, New Jersey, on 30 October.

The flight suffered a control problem and a sudden uncommanded drop in altitude, basically a sharp loss of height, which left 15 passengers with injuries and forced the flight to make an emergency landing in Tampa, Florida.

After investigating the incident, Airbus said "intense solar radiation" may corrupt data critical to the functioning of flight controls.

The issue is known as bit flip, where solar radiation can strike a computer's memory, changing its data from a 0 to a 1 and vice versa - a risk which also affects spacecraft.

Read more: Which airlines are affected by Airbus disruption?

'Very concerning' - but 'very low likelihood' of such an event

The situation was "very concerning", travel expert Simon Calder told Sky News presenter Gillian Joseph.

However, he said there was a "very low likelihood" of such an event happening, adding: "In aviation, nothing is taken for granted."

He said: "Aviation remains extraordinarily safe. And that is partly because as soon as a possible threat is identified, then action is taken immediately."

What is the fix?

The fix involves reverting to earlier software, but must be carried out before the planes can fly again, according to a bulletin to airlines.

Airbus said for most of the affected aircraft, the required update would only take between two to three hours.

However, some jets may need to have their hardware replaced to adopt the required software - a process which would take a longer time.

The Airbus bulletin traced the problem to a flight system called ELAC (Elevator and Aileron Computer), which sends commands from the pilot's side-stick to elevators at the rear of the plane, Reuters reported.

Those elevators control the aircraft's pitch or nose angle, determining which way it is flying.

The A320 was first launched in 1984 and is the main competitor to the Boeing 737 MAX, which was grounded worldwide between March 2019 and December 2020, as well as during January 2024, after fatal crashes in 2018 and 2019 caused by faulty flight-control software.

"Either they can't get pregnant, or they lose their [foetus] over time.

"So, women are afraid of getting pregnant."

For centuries, the indigenous Munduruku have lived in an area across what is now the states of Amazonas and Para in northern Brazil, especially around the Tapajos River.

But in recent decades, villagers had been plagued by curious symptoms that they didn't realise could be related: children unable to lift their heads, adults unable to walk any more, muscle tremors, memory loss, fading hearing and vision, miscarriages.

Now they are finally closing in on the cause.

The Tapajos river, their lifeblood, is laced with highly toxic mercury.

Mercury poisoning is hard to diagnose because symptoms resemble other degenerative illnesses like Parkinson's or Alzheimer's, says Gabriela Arrifano, professor of mercury toxicology at the Federal University of Para.

"But there is now enough evidence to relate the signs and symptoms found in people exposed to mercury."

And they have no doubts about where it's coming from.

"We have robust evidence that mercury emissions to the environment comes from illegal gold mining activity," says Prof Arrifano in her university lab, where she analyses hair and blood samples.

When researchers began studying the symptoms, Alessandra "didn't know what mercury was", she says.

Hand in hand with drugs

In Brazil, gold mining is outlawed in indigenous territory.

Yet swathes of it are pockmarked with red and orange craters from illicit gold projects - a trend fuelled by record-high prices around the world.

The underground trade works hand in hand with organised crime groups, sharing the same makeshift runways and roads through the Amazon rainforest, and using the gold to launder drug money.

The gold, once locked in the mountainside of the Andes, was gradually washed away by ancient rain into the Amazon basin.

To extract it, illegal miners churn up the riverbed and combine it with mercury because it binds to gold.

The process releases mercury into the air, water and soil.

Over time, the mercury coursing through the waterways accumulates in river fish, which indigenous communities eat for breakfast, lunch, dinner.

One study found one in five fish in markets in northern Brazil had dangerous levels of mercury (0.5 micrograms per gram).

Once in the guts, it enters the bloodstream and makes its way to the brain, where it can cause lesions.

Even low levels of exposure can disrupt most of the body's systems, whether reproductive, skin, or nervous systems.

Prof Arrifano says people's visual field shrinks so they lose their peripheral vision. "And then you can imagine this is very hard for people who live in the forest that need their complete senses."

The Munduruku have been fending off mining on their land since 1960s, Alessandra tells Sky News in Para's state capital Belem, as the city hosted international climate talks.

Her symptoms aren't so bad. "I feel tingling in my hands, brain fog, forgetfulness, that is because of the mercury."

But her niece can't walk or talk.

Alessandra suspects it's got something to do with the girl's grandfather being a fisherman.

"So maybe because of this, the mother ended up ingesting a lot of mercury in her body that went to the child."

The toxic metal also accumulates in placentas, breast milk and children, often two or three times the safe threshold for pregnant women.

One study across all of Brazil identified 668 cases of mercury poisoning, but that's thought to be a vast underestimate due to poor data collection and lack of access to healthcare.

How global gold prices fuel the problem

The current administration under President Luiz Inacio Lula da Silva has been attempting a widespread crackdown on illegal mining.

Its environmental protection agency, IBAMA, swoops in by helicopter, blows up equipment, torches makeshift buildings and flies out again.

It has also frozen assets and ended the presumption of "good faith" - that gold for sale was extracted from lawful sights.

In the Yanomami Indigenous Territory in the far north, federal government figures show a 94% reduction in active illegal mining areas between 2023 and 2025.

But some of these miners have set up camp elsewhere, and the ever-soaring price of gold is making it "harder" to combat, one of Brazil's top officials admits.

"We thought that the amount would be reduced, and initially it did," Adalberto Maluf, national secretary for water resources in the environment ministry, overseeing the crackdown, tells Sky News in Belem.

"But I think it's not going as fast as we wanted, or we thought it could happen, mainly because the price of gold continues rising."

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The problem is not unique to Brazil, but common across South America and parts of Africa.

Prices are surging as investors seek security from market turbulence and geopolitical tensions - upping the incentive for miners despite the risks, says Julia Yansara from the Financial Accountability and Corporate Transparency Coalition.

"It is driving illegal gold miners into new areas. And it's driving new criminal groups to get involved in this for the first time."

'If we don't fight, we are crushed'

The Munduruku were formerly known as an aggressive group, feared by neighbouring peoples, before being fought down by colonisers who annexed their territory.

This year, they capitalised on the global attention on Brazil as it hosted the UN climate talks (COP30) to fight for their land once again.

Halfway through the conference they peacefully blocked the entrance, forcing a meeting with officials that then won them the legal rights to two further portions of territory.

When the land is demarcated, it's easier to pressure the government to protect the land, says Alessandra.

"If we don't fight, we are crushed, we are taken over."

But she too knows they are fighting a rising tide.

"When the price increases, everyone wants to invade our land, to pollute the water, to destroy the forest, because they need to take the gold to sell to other countries."

But those buyers don't know "what is happening to our bodies, to our lives", she adds.

In her speech in the House of Commons on Wednesday, the chancellor said she was backing small businesses by introducing "permanently lower tax rates for over 750,000 retail, hospitality and leisure properties - the lowest tax rates since 1991".

But while the government gave itself the powers to discount the business rates bills for high street businesses through legislation earlier this year, the chancellor only implemented a reduction of a quarter of what the government is able to, and she is being accused of imposing a "stealth tax".

It has left small retail, hospitality, and leisure businesses questioning whether their businesses will be viable beyond April next year.

A Treasury spokesperson said: "We're protecting pubs, restaurants and cafes with the budget's £4.3bn support package - capping bill rises so a typical independent pub will pay around £4,800 less next year than they otherwise would have.

"This comes on top of cutting licensing costs to help more venues offer pavement drinks and al fresco dining, maintaining our cut to alcohol duty on draught pints, and capping corporation tax."

Business rates, which are a tax on commercial properties in England and Wales, are calculated through a complex formula of the value of the property, assessed by a government agency every three years, combined with a national "multiplier" set by the Treasury, giving a final cash amount.

Over the last few years, small businesses were given business rates relief of 75% to support them over the COVID pandemic, and Ms Reeves reduced that to 40% at last year's budget.

The idea was that at the budget this year, the chancellor would remove that remaining relief in favour of reforming the business rates system to compensate for that drop, while shifting the tax burden on to much bigger businesses and companies like Amazon with lots of warehouse space.

However, the chancellor only announced a 5p in the pound discount for small retail, hospitality, and leisure businesses, rather than the assumed 20p drop which the government gave itself the powers to implement, and which trade bodies had been lobbying for.

On top of that, small businesses have seen the government-assessed value of their property increase dramatically, which wipes out the discount, and sees their business rates bill shoot far above what they had previously been paying.

One pub owner near Hull, Sam Caroll, has seen the assessed value of one of his two properties increase from £67,000 to £110,000 in just three years - a 64% increase.

He told Sky News that there is a "continual question" of business viability, and while he thinks they can "adapt" in the short term, "there will be a tipping point at some point". Even at the moment, packing out their pubs seven nights a week, "it's difficult for us to break even", he said.

There will be a discount for small businesses to transition to the higher business rates level, but by year three, almost the full amount is expected to be payable, and Mr Carroll described it as "getting f***** slowly, instead of getting f***** overnight".

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Sean Hughes, who owns multiple hospitality venues in St Albans, has also seen vast increases in the assessed value of his properties, and was sharply critical of the transitional arrangements the government is implementing.

He told Sky News: "Fundamental business rate reform was promised and we have total chaos. If [the system] was fair, why would they need transitional relief periods?"

A spokesperson of the Valuation Office Agency (VOA), which assesses the value of commercial properties for business rates purposes, told Sky News: "At the last revaluation, some sectors including hospitality were significantly affected by the pandemic, which resulted in much lower rateable values than they would have seen otherwise. Businesses that have now seen a recovery in trade are also likely to see an increase in their rateable value."

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However, Sky News has seen evidence of businesses whose assessed value did not decrease when assessed during the pandemic, but actually rose, and has risen dramatically this year.

Data compiled by the Pubs Advisory Service, shows that the number of pubs in the UK has decreased by nearly 5% in three years, but the average value of the properties has risen by an average of 36.82% per pub.

And analysis by UK Hospitality, the trade body that represents hospitality businesses, has found that over the next three years, the average pub will pay an extra £12,900 in business rates, even with the transitional arrangements, while an average hotel will see its bill soar by £205,200.

The body adds that by 2028/29, an average pub's business rates will have increased by 76% and an average hotel's by 115%, compared to 16% for a distribution warehouse like the ones the web giants use.

It's not just the business rates rise that is worrying owners - it is the increase in employers' national insurance implemented at the last budget, the increase in energy bills over the last few years, and the rise in the minimum wage, particularly for young people.

With the budget set to squeeze disposal income, there is little room for price increases to make up the shortfall either.

In a letter to the chancellor on Friday, Liberal Democrat deputy leader Daisy Cooper said small business owners "have been pushed to tears as they're hit with the bombshell of higher business rates bills", noting that "the government has chosen not to use the full powers it gave itself to throw high streets a lifeline".

She added that businesses had been promised "permanently lower business rates", but it appears the government has "broken yet another promise, by imposing a stealth tax not just on people, but on treasured high street businesses too", and called on ministers to "throw our high streets and Britain's hospitality sector a lifeline".

Conservative shadow business secretary Andrew Griffith published his own analysis of the government's budget measures on Friday morning, that found they will "hammer British pubs".

Of the chancellor, he said: "She pretended in her budget speech to be supportive, whilst the true detail is that a combination of rate revaluations and scrapping reliefs will leave most pubs paying thousands of pounds more than they cannot afford."

Kate Nicholls, Chair of UKHospitality, said in a statement: "The government promised in its manifesto that it would level the playing field between the high street and online giants. The plan in the budget to achieve this is quickly unravelling, and will deliver the exact opposite."

She said they "repeatedly warned the Treasury" of the impending impacted of the value reassessment, but nonetheless, hospitality businesses are now facing "eye-watering increases".

She added: "We agree with its reforms to deliver permanently lower business rates for hospitality and we appreciate the package of transitional relief, but its current proposal is not delivering lower bills. A 20p discount for hospitality would. We urge the chancellor to revisit."

Yet for all their wizardry, AIs can also be quite useless. They make things up and misunderstand instructions. They are brilliant as toys but incompetent as assistants.

All this makes it hard to know how to put AI into perspective. Is it the most important technological trend since the iPhone? Or since the industrial revolution? At this distance, it's hard to say.

There are industry measures to assess the intelligence of AI models, known as benchmarks. These too show rapid improvement.

When Google released Gemini 3, its latest AI upgrade, last week, it broke records across the board.

But benchmarks are too narrow to be totally reliable guides to ability and potential.

This, says Marc Warner, is why you need to zoom out and look at the overall trend. When you do, he says, you see "a very strong exponential".

An exponential trend is where growth doubles and keeps on doubling. At first progress seems slow, but, before long, the line on the chart is rising almost vertically.

"Nothing, nothing, nothing, everything," as Dr Warner puts it.

It's a pattern familiar from the COVID pandemic, where it caught out politicians and public health officials around the world.

Now, says Dr Warner, who runs British tech company Faculty, it's happening with AI - and he's worried we don't have a plan.

"We saw in COVID, if you don't prepare for exponentials properly, they can really hurt you when things start to get very serious," he says.

Could AI be as disruptive as COVID? It depends if its growth keeps going, Dr Warner says, and if AI is good at as many things as it appears to be.

"But if those were true, this would be way bigger than COVID," he says.

"COVID was a temporary shift…This will be a more permanent reshaping of how everything operates."

When will AI top out?

Dr Warner, who trained as a physicist before moving from academia into tech, has been here before.

In March 2020, Faculty was modelling patient data for the NHS. He saw the virus doubling at a faster rate than the government appeared to appreciate.

He got in touch with his brother Ben, who was working as a data scientist in Downing Street.

Late on the evening of 12 March, Ben and Marc explained the situation to the prime minister's chief of staff, Dominic Cummings. Ten days later the country was in lockdown.

"Marc Warner is one of the smartest and most ethical people I have ever met in my life," Mr Cummings later told MPs. "I think that without him thousands of people would be dead."

Eventually, Dr Warner says, AI will stop getting better, simply because the tech companies run out of energy to train their power-hungry models.

"The amount of energy you'd need to train these models would be more than exists on the whole planet," he says.

"So this has to top out at some point."

'Doubling every seven months'

However, the data he's looking at - a comparison of humans and AI models on software development tasks by AI research firm Metr - suggests AI is doubling capacity every seven months and that it's likely "there's at least another five years of this".

So, by his estimate, there are a lot of changes to come.

Some will be hugely positive. But inevitably there will be downsides.

"As with any new technology, there will come a bunch of disruptions… That's why I feel like it's so important to actually think seriously about if this holds true, what it would mean," says Dr Warner.

"We will be able to manage it, but we'll only be able to do that if we actually have a real plan."

Does he think the government has one?

"In the short term, I think the government's actually doing a decent job," he says. "They announced this sovereign AI fund, I think that's a good thing."

He also praises the UK's AI Security Institute, which investigates technical risks.

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Just as in the pandemic, huge uncertainty surrounds even the best forecasts of AI.

Metr's data only measures software development, and only assesses if AI has a 50% chance of succeeding at a task, so it's hard to generalise from.

Then there's the economic uncertainty. There may be a speculative bubble around AI, Dr Warner says, but that doesn't make the underlying technology any less impactful.

"It feels to me something like we've gone from the first [aeroplane] flight to something like Concorde in a seven-year period. And that is a very big deal."

Especially when there might be a lot more to come.