During the late 70s the first Space Shuttle did glide tests after being
launched from the Boeing 747 Shuttle Transporter.

Does anybody know how the Shuttle was released from the back of the 747.
Did the 747 have to (unbelievably!) roll inverted for the release, or did it
pitch down to an extreme attitude or was there some other method?

At what altitude was the glide tests commenced?

cheers

Gordon