The title is a pun on "jet-propelled".
Porky finds out that Daffy got a jetpack for himself, which he called a backpack. When Daffy starts it, Porky scolds him about the flying jetpack wrecking their Looneyville house. When Daffy mentions that he would never let him try on the jetpack, however, the jetpack takes Porky with it. Now it's up to Daffy to fix this jet-propelled predicament.