Overview
- An X5-class solar flare on November 11, 2025 triggered GLE 77, the largest ground-level enhancement in nearly 20 years and produced global neutron-monitor spikes as high as about 800 percent.
- Researchers deployed a coordinated network of UK neutron monitors, detectors on commercial aircraft, and weather balloons to collect the most complete atmospheric radiation dataset ever gathered for a GLE.
- One London–New York flight recorded about a 42–46 percent increase in radiation compared with normal background levels, and balloon data exceeded ICAO’s 'moderate' advisory at business-jet altitudes and 'severe' thresholds at supersonic altitudes.
- The study says immediate risk to passengers was low but warns that cumulative exposure could affect aircrew and frequent flyers and that high-energy particles can cause transient errors in avionics and onboard electronics.
- Authors call for route- and altitude-specific monitoring that combines direct atmospheric measurements with forecasting so airlines can make operational choices such as lowering cruise altitudes, rerouting, or delaying flights; the paper also notes the UK’s new nationwide neutron-monitor network helped enable the rapid response.