 The external wing struts of the F.II were removed, leaving a clean cantilever wing.The trapezoidal windows seen in the Grulich built F.IIs were standard on the F.III.Like its predecessor, the F.III was initially powered by a readily available, war surplus 138 kW (185 hp) BMW IIIa engine, but once again KLM re-engined theirs with the 172 kW (230 hp) Armstrong Siddeley Puma.