The airframe of the A330 features a low-wing lever monoplane with a wing virtually identical to that of the A340-200/300. On the A330-300, one engine is installed at the inboard pylon while the outboard pylon position is not used; for the A340-300, both engine pylons are used, which allows the A340-300 wing to sustain a higher (wing limited) MTOW. This is as the A340's two engines at each wing provide a more equal force distribution (engine weight) over the wing, while also the total engine weight counteracting moment is located more outboard with more engine weight located further outboard on the wing, hence the wing root bending moment with equal TOW is less on the A340-300 than on the A330-300. The wings were designed and manufactured by BAe, which developed a long slender wing with a very high aspect ratio to provide high aerodynamic efficiency.