From: Aerophotos

care to explain what my mate was doing flying a USAF aircraft over the
groom lake airspace and range in combat with "mig -21"was then ?

snip

Ummmm, Groom Lake aka Area 51 didn't exist in the 70's. That's the story
and
we're sticking to it.
Dave

I could be wrong but I would venture to say Dave was joking.

Take a look at the charts for that time frame. The area is blank. The
government denied it existed. No one who worked there was allowed to
talk...etc.

Dan, U. S. Air Force, retired