MGM Grand Air was the follow up to Regent Air, whose 727s went on to serve for MGM Grand Air upon Regent Air's demise. Interestingly, I too flew one of those MGM Grand 727s, though it was in the service of Braniff International before being sold to Regent Air.
Thanks, macabus, for the stroll down memory lane. Flying around America sure was alot more fun back in those days.