As others have mentioned, in WWII, many of the things modern militaries take for granted were in their infancy. In modern times, there are lots of staff meetings and procedures involving nothing other than deconflicting fires. Fast jets hit this, artillery hits that, fighters cover here, surface-to-air assets cover there, etc.

But those lessons are written in blood due to exactly incidents like the one you mention. The "big sky, little airplane" theory is not something to bet your life on.