In this question, concerning the airports that serve the most countries, domestic flights are excluded (i.e. the country containing the airport should not contribute to its destination count).
This leads me to wonder - are there any examples of airports where this wouldn't make a difference to the score, as they don't have any domestic flights?
An obvious case would be countries that are simply too small to have more than one airport; those qualify, but should probably be noted as such. More interesting would be countries with multiple airports, at least one of which for some reason lacks domestic services.
As to which flights count, same rules as the original:
Flights must be regularly scheduled, although they can be seasonal, and available to book for individual passengers, to exclude chartering an airline and private flights.