Airside layover
You change planes without passing immigration.
UN tourism statistics
Doesn’t countTransit passengers are visitors only if they make a stop and enter the country’s legal territory. Staying airside, you don’t enter.
Source: IRTS 2008, para. 2.61Travelers’ Century Club
CountsLeaving the plane is enough. The rule accepts even “a plane fuel stop, provided that you disembark” and set foot in the territory, and doesn’t mention immigration.
Source: TCC countries and territoriesMost Traveled People
Doesn’t countAsked whether an airport transfer counts, MTP answers “no.” Where passport control exists, you must enter through it.
Source: MTP rules for visitsNomadMania
Doesn’t countVisits involving airports don’t count, “irrespective whether immigration is crossed or not.”
Source: NomadMania rules, section 2