[chrisper]

If there is fog you do not fly by hand. You use an automated landing system (ILS) in that case.

[jiqiren]

SFO's ILS isn't always functioning. It was turned off for months when Asiana crashed (June 1st - Aug 2nd)[1].

[1] http://www.popularmechanics.com/flight/a9124/what-went-wrong...

[mikeash]

I'm pretty sure SFO always has functioning ILS, otherwise the airport would have to close every time there was even mildly bad weather. Each runway has its own system, though, so an individual runway's ILS can be turned off.

If there was fog, they wouldn't have been using 28L.

[bake]

ILS does not entail automation -- it provides guidance to humans operating the controls.

[dingaling]

ILS does not necessarily indicate automation, but about 5% of ILS approaches are autolandings.