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.
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.
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.