1929 Waco ATO, Pilot: Dennis Guentzel. Dennis flew for Northwest Airlines for 30 years and retired in 1998 with about 21,200 hours. Prior to his NWA career, he spent some time as an instructor mostly in Pipers, most every model from Tri-pacer to AztecÕs, as well as some Cessna products. Since then Dennis has been happily flying his Waco.