EFVS — where it earns its keep

An Enhanced Flight Vision System (EFVS) lets a suitably equipped aircraft continue an approach in visibility that would otherwise force a diversion, by imaging the runway environment with infrared sensors on a head-up display. Under FAA 14 CFR 91.176 and equivalent EASA rules the credit is worth the most at airports that are frequently fogbound and lack CAT II/III ILS — where a conventionally equipped aircraft has no lower minima to fall back on. This table ranks those airports by the hours per year an EFVS-equipped aircraft flying to CAT I minima could recover (visibility between roughly 300 m and the airport's CAT I floor). Validation: US DOT/BTS on-time data (13.9M departures, 2023–24) shows flights scheduled during EFVS-recoverable hours were weather-cancelled at 5.2× the baseline rate — read as validation that these hours are operationally hostile, not as a fog-specific cost model.

September is in season — these airports together average about 1,368 hours below CAT I minima in September, against 1,847 in December, the peak month.

Regulatory permission (FAA 91.176, EASA equivalents) to descend below published minima and, with the right equipment and training, to land using the enhanced vision image instead of natural vision of the runway environment.

At airports with many sub-CAT-I hours and no CAT II/III ILS: without the deck-side credit those hours are diversions. The ranking above is that intersection, computed per airport from ten years of observations and published approach capability.