Quantifying the full extent and attribution of dose reduction during the UAL 990 Gannon-storm deviation

Ascertain the full extent of the total effective dose reduction achieved by rerouting United Airlines flight UAL 990 on May 10–11, 2024 to lower altitude and lower magnetic latitude during the Gannon storm, and quantify the relative contributions from magnetic cutoff rigidity (geomagnetic shielding), the Forbush decrease in galactic cosmic ray flux, changes in cruise altitude (atmospheric shielding), and any contemporaneous solar energetic particle exposure.

Background

The study compares two SFO–CDG flights (May 2024 during a G5 geomagnetic storm and June 2025 during quiet conditions) that carried the same ARMAS FM7 instrument. Surprisingly, total effective dose was lower during the storm flight, likely due to a Forbush decrease and deliberate operational choices (lower altitude and latitude).

The authors explicitly state that the full extent of the dose reduction cannot be exactly calculated from their comparison and indicate that multiple factors likely contributed, but their quantitative attribution could not be resolved. This leaves an explicit open task to perform a rigorous quantitative decomposition of the observed dose reduction.

References

While the deviated UAL 990 route on May 10-11, 2024 during the extreme Gannon storm to lower altitudes and lower latitudes contributed to noticeable total effective dose reduction for the entire flight, and while a Forbush decrease also removed a population of lower energy GCR particles that, had they been present, would have increased the overall total effective dose, the full extent of the dose reduction cannot be exactly calculated.

— Advances in aviation radiation mitigation were demonstrated during the Gannon storm  (2507.00887 - Tobiska et al., 1 Jul 2025) in Section 4.1, Radiation reduction