Like Koolhovens earlier F.K.23 Bantam, the Basilisk was a two-bay biplane with a wooden monocoque fuselage, but was larger and heavier to accommodate the larger engine and the equipment required by the Specification. Armament was two Vickers machine guns mounted ahead of the pilot, and enclosed in a large fairing that formed the upper coaming of the pilot's cockpit.
Three prototypes were ordered in early 1918, and the first one flew in September 1918. It was destroyed on 3 May 1919 when attempting to break the World altitude record, its engine catching fire and BAT's test pilot, Peter Legh, being killed. The second and third prototype were fitted with modified, horn balanced ailerons, with the second prototype tested at Martlesham Heath in October 1919. While its performance was good (although not as good as claimed by BAT), the Dragonfly engine was hopelessly unreliable, with further development or production abandoned earlier in the year, and the Basilisk was abandoned when Koolhoven left BAT at the end of 1919.