Amazing, so few or our enemies truly understood at what capacity we could wage war. There is a similar production film related to building a new factory to manufacture tanks, I would expect that for every part or necessity of the war effort.
Henry Ford was an early pioneer of the concept of the "production line" when he used it to construct the Model "T" Ford, at an affordable price and which you could have in any colour as long as it was black.
It is interesting to see that the spot welding of aluminium was used to speed up production as an alternative to drilling/riveting in order to join aluminium parts/panels together more quickly. They must have had close and strict quality control processes in place for the spot welding because it was aluminium which is more difficult to successfully spot weld than steel and also because it was for aircraft use and, therefore, potentially safety critical.
As much as I've read about history or at least how much I think I have read I was surprised even stunned when at the 27:00 minute mark they showed how production used a "midget" to climb into the wing to attach the outer wing to the wing structure assembly containing the engines. I knew they used slighter people, many of whom were women to assemble or complete assemblies that contained tight or restrictive spaces, but had not seen them use as they said midget's; apparently everyone had a part in the logistics chain.
My dad was a ground crew chief for B-24's in the Pacific with the 5th Army Air Force. The hardest repair on a B-24 was to find a shrapnel leak in a self sealing fuel bladder in one of the wings. It was a huge chore just to get the bladder out of the wing because of all the cross members in the way. Then once found and repaired was the next hard step to get it back in.