Flight safety implications of the extreme solar proton event of 23 February 1956

•The two solar event models produce very different dose-vs-cutoff rigidity profiles.•Aviation solar event doses exceed 10-h galactic doses where cutoff rigidity is low.•Galactic 10-h doses exceed solar event doses where cutoff rigidity exceeds ∼4 GV.•Galactic 1-h doses exceed solar event doses where cutoff rigidity exceeds 6.4 GV.