 Unfortunately these intakes led to elevator blanking on formation of shock waves, and three aircraft and pilots were lost in unrecoverable dives.All of the Nene-engined aircraft were later modified to move the auxiliary intakes beneath the fuselage, thus entirely avoiding the problem.In June 1949, the first Vampire F.30 fighter ("A79-1") made its first flight; it was followed by 56 more F.30 variants before the final 23 aircraft were completed as FB.31s, being fitted with strengthened and clipped wings along with underwing hardpoints.