The strongest solar radiation storm in nearly 20 years pushed radiation levels past aviation safety thresholds at high altitude over northern Britain, Physics World reports. Despite exceeding those limits, authorities issued no warning to airlines or crews flying through the affected region.

The episode exposes a little-noticed vulnerability in atmospheric radiation monitoring: solar energetic particle events can abruptly raise the dose received by passengers and crew on high-latitude, high-altitude routes, precisely where Earth's magnetic shielding is weakest. Safety limits for occupational and public exposure have long existed, but their practical application depends on monitoring systems detecting and communicating the event quickly enough.

In this case, however, the radiation increase did not translate into an operational alert, raising the question of whether current monitoring and notification protocols are sized for events of this magnitude, which become more likely as the Sun approaches the peak of its activity cycle. Experts consulted by Physics World note that the combination of polar routes, long-haul flights and intense particle storms warrants a review of thresholds and response times.

It remains to be determined how many flights were actually affected and what doses the most exposed crews received, and whether early-warning systems should be reinforced for future extreme solar events.