I can guarantee, that even if those FW190's were buried in cosmolene wrappings in the late 1940's, they'll be well and truly Focked by now.
Cosmolene is good for about 20 years at its very best, without being buried. I've unwrapped many a part that was over 20 yrs old, that had been factory-wrapped in cosmolene-soaked paper - and corrosion on the part was still common, even when the part had been shelf-stored.
The simple problem is that alloys are highly reactive, high-grade steels corrode overnight just with a sideways look - let alone poor storage - and burying items is a guaranteed method of ensuring destruction and decomposition within a few years.
The only component I have ever seen dug up and used again after being buried, was a set of crawler tractor tracks for an antique Caterpillar tractor.
They had been buried in relatively dry soil (in California), but they still had substantial corrosion on them - however, the sheer thickness of the metal in the tracks enabled them to be utilised again after sandblasting.