 The space enclosed by a set of interplane struts is called a "bay" (much as the architectural form is used), hence a biplane or triplane with one set of such struts connecting the wings on each side of the aircraft is a "single-bay biplane".This provided sufficient strength for smaller aircraft such as the First World War-era Fokker D.VII fighter and the Second World War de Havilland Tiger Moth basic trainer.The larger two-seat Curtiss JN-4 Jenny is a "two bay biplane", the extra bay being necessary as overlong bays are prone to flexing and can fail.