Vintage Wings of Canada has published a magnificent article on its Web site titled 'Manufacturing Victory: An Homage to the Aircraft Assembly Line'. It contains dozens of photographs (many of which I've never seen before) showing aircraft factories and assembly lines in the USA, Britain and Germany. Here are a few examples to whet your appetite, reduced in size to fit this blog.
There are many more (and larger) images at the link. Pure nostalgia for aircraft buffs!