The pilots would execute untowered approach procedures, a small airport with little to no traffic and VFR flight you may self-announce on frequency, a larger airport you go back to approach, etc.

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tadfisher 3 hours ago | parent [-]

Each of those flights should have an alternate and be prepared (have enough fuel) to divert. If there is a fuel emergency then self-announcing is likely appropriate as the plane is coming down anyway, but that is multiple things going wrong.

	▲	bombcar an hour ago \| parent [-]
		A big part of it is what category of airport it is, and plane. General aviation almost always goes to self-announce (which includes some business jets perhaps, they often land at untowered airports) but not category 135 air travel or whatever it is.