[A CA Guy]

Right, so IMO they would try to pick a time when most of the flights were over land to rain metal from a plane explosion.
The rest would be killed en route over the ocean.

That is what makes sense to me anyway.

[The Red Zone]

But, rain metal on what. Virtually all of a flight is not over any densely populated area. You know, that's why they call it fly over country? And flight schedules are notorious for being late by wildly varying amounts of time (never heard of one being early yet).