William Harwood Juvonen, 81, a long-time aircraft salesman and co-founder of charter and aircraft management firm Flight Services Group, died December 22 at his home in Stamford, Connecticut.A regular NBAA convention attendee, Juvonen had a corporate aviation career that spanned more than 40 years and led him to sales positions involving Pan Am Business Jets, Cessna Citations, and Canadair Challengers. Ultimately, he helped found and became chairman of Flight Services Group, which grew into one of the larger charter and management firms that was later acquired by PrivatAir.Born in Santa Ana, California, Juvonen joined the U.S. Marine Corps after graduating from Stanford University. He was trained as a carrier-based fighter and helicopter pilot, attending the Replacement Air Group, later known as Top Gun. He flew the supersonic F8-U Crusader.Later he joined Pan American World Airways as a sales manager for Pan Am Business Jets. He then became a sales manager for Cessna, introducing the Citation series, beginning with the 500. Jumping from the success of the introduction of the venerable Citation line, Juvonen introduced the Canadair Challenger 600 program as vice president of sales. He joined Polaris Aircraft Leasing as v-p of marketing before helping establish Flight Services Group.He is survived by his wife, Karen Coleman Juvonen, and children Nancy Juvonen Fallon (Jimmy) and Jim Juvonen (Sarah), along with five grandchildren.