In 1967 Griggs entered the U.S. Naval Test Pilot School at Patuxent River, Maryland and upon completion of test pilot training was assigned to the Flying Qualities and Performance Branch, Flight Test Division, where he flew various test projects on fighter and attack-type aircraft.
He logged 9,500 hours flying time, 7,800 hours in jet aircraft, and flew over 45 different types of aircraft including single and multi engine prop, turboprop and jet aircraft, helicopters, gliders, hot air balloons and the Space Shuttle.