I never saw either of them at Kadena.
They're really time machines from the future. One crashed in my backyard when I was 12 and I found its flux capacitor. They're not really aliens, just evolved humans looking for good DNA to revive the human race after the Eugenics Wars decimated everything and turned us all into Carville-clones.
In 1970/71, Blackbirds were at least occasionally at Okinawa.