Paul,
For my money, it was the best cartoon Hanna Barbera ever made. It was only on for one season, because animation was done by hand back in the 1960's, so the level of realism employed to make Johnny Quest was prohibitively expensive. It was an action/adventure series, with some great aircraft depicted, from a Sopwith Camel and Fokker DR1 in an episode about an evil WWI ace, to a DeHaviland Tiger Moth in an episode about them discovering cavemen on top of a mountain in Africa. My favorite episode, Turu the Terrible, has them on the "Amazon Queen" (a steamboat copied from the African Queen of Bogart/Hepburn fame) when they are attacked by a pterodactyl that somehow survived from dinosaur times and became the pet of a mad scientist confined to a wheelchair. I think you would definitely enjoy catching an episode or two.