aliens have been there for a good long while now just so happens the government finally released what we've known. I would imagine they have transcended actual speech and simply telepathy the language we are most familiar with... now all we need is a cricket gun to keep those things inline! (MIB)
The entire territory of the US and UK + the Netherlands is one continuous testing ground for secret aircraft. Moreover, these testing grounds are preferred by the most populated states and provinces. Arizona? No! Only NYC and Miami! Or London at least.
Neither in the USSR nor in China there have never been any tests of something flying