At it’s production height, the Ford factory at Willow Run was completing one B-24 bomber an hour, 24 hours a day, seven days a week. That’s how you fill a sky with planes.
It’s amazing how many planes (and tanks, and ships) were built in that few year period — and what planes (and tanks, and some of the ships) didn’t get destroyed were scrapped before 1950. Just the scrapping effort dwarfs a lot of activity done before and since. :’) Just combat planes, the US alone built 236,305, kind of a lot, really.
http://en.wikipedia.org/wiki/United_States_aircraft_production_during_World_War_II
http://en.wikipedia.org/wiki/Military_production_during_World_War_II