Don't know where I'm going, all I know is I'm flyin'

from Wiz Khalifa – O.N.I.F.C. Lyrics on Rap Genius

This means that he doesn’t know where he is going next, but he knows he’ll be high.

He has made multiple references to being high in past songs. He even has a mixtape with the title “Flight School.”
Obviously he isn’t a pilot, as in T.A.P. (Take A Plane):

Roll it up, light it up, have a puff, let’s take a plane"

again, Wiz is not taking a plane, he’s rolling up a joint and smoking it.

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