Shortest and longest flights on Mumbai-Delhi route have a variation of up to an hour

When social media was still new, one of the first viral videos doing the rounds was of a Pakistani reality show host on the streets asking people why an airline takes 90 minutes to go to Karachi from Islamabad but one and a half hours on the return. The answers, as expected, were funny.

While searching for a flight between two cities, airlines and OTAs (Online Travel Agencies) give options to sort the flights by departure time or duration. While the duration aspect might sound nice for a one-stop flight, it should ideally not make a difference for a non-stop flight. This is actually wrong!