When is the word "Departure" countable or uncountable? [closed]

When is "Departure" a countable usage and when is it not?

There is some disagreement between dictionaries about whether the noun "departure" can be uncountable or not. Cambridge says it is countable, Mirriam-Webster doesn't say (which I assume means it defaults to countable). Only Wiktionary and Oxford learners say it can be uncountable.

The only example I can find in the dictionaries that would seem be fit 'uncountable" is where it is used to refer to a part of many events, for example:

You must check in at least one hour before departure.

Here "departure" doesn't refer to a single event but is used to refer to implicitly one of many departures. Other dictionaries quote similar structures but consider the noun singular or countable.