"Apart from the time required to train pilots, and the time they're off duty during training, it may get expensive for airlines to train all their pilots for fog-like conditions. Plus, it's a small duration during an entire year when fog sets in, and the occurrence is limited to major northern airports like Delhi only," the person added.
Echoing a similar view, Joshi said the phenomenon of fog is largely Delhi-centric. “Airlines may think that we only have conditions of extreme fog on a few days every year, and spending a pilot's time and the airline's money on training can add up to its expenses. So, they may prefer holding it for a few days," he said. Delhi Airport has two CAT IIIB-compliant runways, one currently under maintenance.