 The larger more capable Royal Aircraft Factory R.E.7 was a further development of the design.Some modified single-seat high altitude aircraft were built with extended-span (57 ft 2⅓ in or 17.43 m) upper wings supported by a pair of outward-leaning struts.Other R.E.5s were used for experimentation with airbrakes and for test flying the Royal Aircraft Factory 4 engine.