Why did the terrorist masturbate and smoke weed on the plane?
He was told to high-jack it.
High-jack
Explanation
Explain Bear
Listen up, buttercup! This joke is playin' on words, see? "High-jack" sounds like "hijack," which is what terrorists do with planes, but it also sounds like bein' high on weed while you're jackin' off. Get it now, dummy?