A rare ‘solar radiation storm’ soaked people aboard a London to New York flight with more radiation than normal, researchers say.
In November, Earth was lashed by sun particles so powerful they pierced the planet’s layer-cake atmosphere and invisible barrier, the magnetic field.
It caused the strongest ‘ground-level enhancement’ event in more than two decades, with radiation spiking well below the skies.
During this, a 11.45pm flight from Heathrow experienced a 42.6% increase in radiation, according to the study published Tuesday in Space Weather.
By solar storm standards, that was a ‘modest’ event, Dr Ben Clewer, a space weather expert at the University of Surrey and the paper’s co-author,tells Metro.
‘In a larger event, the immediate operational concern would not only be personal doses,’ he says.
‘High-energy particles can also interact with aircraft electronics and cause errors, including temporary “bit flips” in avionics and other onboard systems.’
Do holiday-makers have anything to worry about?
Behind this storm was an X5-class solar flare – one of the strongest classifications of when the sun’s magnetic field twists and snaps.
This sent an ‘unusually large number of high-energy particles’ into space, Dr Clewer says, that splattered Earth at 11.20am on November 11, 2025.
When this solar gunk hit, the resulting geomagnetic storm disrupted power grids and radio systems in Europe and Africa.
Machines built to monitor neutrons – one of the particles spat out by the sun – went haywire, from Mexico and Antarctica to Cornwall and Shetland.
Some pinged 800% more neutrons per hour than they normally do, according to the National Oceanic and Atmospheric Administration.
The Met Office and the Royal Netherlands Meteorological Institute (KNMI) measured the solar storm in real time using weather balloons.
By using all this, researchers created the most comprehensive dataset ever from Earth’s atmosphere during a solar radiation event.
They found that flight paths at mid-high latitudes, such as northern-transatlantic or polar trips to and from Japan, were more vulnerable.
How high a plane was flying during the storm was also a factor.
The International Civil Aviation Organisation issues advisories if space weather could cause an ‘enhanced radiation dose at specific flight levels’.
The paper found that the radiation on November 11 smashed the ICAO’s ‘moderate’ advisory threshold at business jet altitudes, which are higher than commercial jet altitudes, several hours after the storm peaked.
At higher altitudes where supersonic flights tear through the sky, radiation measurements broke the ICAO’s ‘severe’ threshold.
Dr Clewer says as alarming as this sounds, the event was ‘relatively modest’ as it didn’t cause aviation disruption or pose a risk to passengers.
‘The greater, longer-term concern is for aircrew and very frequent flyers, whose exposure accumulates over many flights,’ he warns.
‘The long-term risk should not be overstated, as ionising radiation is a recognised hazard, which is why airlines should assess and monitor crew exposure and adjust rosters where appropriate.’
He also stresses that while the storm caused a ground-level enhancement event, people on the ground had nothing to worry about either.
‘This was extremely minor and only for a few hours, so it was nothing to be concerned about, especially compared to the normal background radiation that everyone receives over the course of a year anyway,’ Dr Clewer says.
Airlines ‘should cancel flights during significant solar radiation storm’
The November 11 solar radiation storm won’t be the last.
Strong solar flares happen two or three times each 11-year solar cycle, when its magnetic poles flip, as if Earth’s north and south poles switched.
So airlines should treat space weather the same way a pilot checks for storms, fearing turbulence or worse, Dr Clewer says.
Space-weather alerts, radiation models and measurements from aircraft and the atmosphere should all be checked before deciding to take off.
If a powerful solar storm is swirling in the skies, airlines should reduce cruise altitude, reroute away from higher latitude regions or cancel flights.
Ensuring the safety of holidaymakers and crew requires better-coordinated radiation monitoring, Dr Clewer adds.
Current space weather advisory systems mostly rely on ground- and space-based observations, but the Surrey researchers plugged the gap with weather balloons
‘Overall, the immediate passenger risk from the November 2025 event appears to have been low,’ Dr Clewer adds.
‘The wider lesson is that a sufficiently severe solar radiation storm could make radiation management a genuine aviation-safety issue, and that modern aircraft operations need reliable, route-specific information when such an event occurs.’
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