Super Jet is a term used to describe something that is incredibly fast, powerful, efficient or impressive. So, to come up with antonyms for the term, we need words that describe things that are slow, weak, inefficient or unimpressive. Some antonyms that come to mind include: slowpoke, weakling, slug, snail, turtle, dawdler, underperformer, and plain Jane. Other antonyms that could be used depending on context might include average, mediocre, ordinary or subpar. Regardless of the word chosen, it should contrast with the power and speed implied by the term Super Jet.