r/steve_martin

I need help identifying a comedy episode that Steve Martin appeared in after 1977 or 78. As I recall this episode, there was a scene where he was dressed up as a confederate soldier. I also think it’s important to know his hair was gray because in the early 70s it was dark. so I know it was a late 70s episode. The joke was as he was leaving to fight in the civil war he was singing to a southern belle “I’m leaving on a jet plane, I don’t know… What a jet plane is“. i thought it was the carol burnett show, but a haven’t found an episode like that. I’d appreciate any help.