No, it's in BoEM, page 24, as a new sor/wiz spell and it is listed as 7th level. T&B lists it as 6th level (and 5th in the spell description, which I think must be an error). BoEM II does not list Mass Fly on the alt.sorcerer list at all, let alone as 7th level. You must be thinking of the first BoEM.