Intended as a replacement for the Junkers Ju 86 in service with the Swedish Air Force,[2] the requirement that led to the Saab 18 called for a three-seat fast reconnaissance aircraft.[3]AB Svenska Järnvägsverkstädernas Aeroplanavdelning (ASJA), SAAB, and AB Götaverken (GV) submitted designs for consideration by the Swedish Air Force.[2] GV's GV8 appeared to be the best suited to the requirement; however, its cost and the departure of their chief designer resulted in SAAB — the company having merged with ASJA in the meantime — being awarded a contract for development of their design.[2]As a number of Americans were on the design staff of SAAB and ASJA,[4] the Saab 18's design shared some similarities with American designs.[2] The outbreak of World War II in 1939 led to a change of priorities by the Swedish Air Force, and production of the Saab 17 was accelerated, at the expense of work on the Saab 18,[2] which, along with a change of requirements that added the role of medium bomber to the specification, resulted in the first flight of the aircraft being delayed until 19 June 1942.[3]Manned by a crew of three — a pilot and navigator under a glazed, offset canopy, and a bombardier in the nose[3] — the Saab 18 prototype was a mid-wing monoplane with twin vertical stabilisers,[3] and was powered by two Pratt & Whitney R-1830 Twin Wasp radial engines.[3] Armament consisted of three 13.2-millimetre (0.52 in) machine guns, one fixed firing forwards and controlled by the pilot, the others being in flexible defensive mounts for use by the navigator and bombardier.[2] Up to 1,000 kilograms (2,200 lb) of bombs could be carried in an internal bay, while up to eight 50-kilogram (110 lb) bombs could be carried on underwing hardpoints.[2]Flight testing showed that the aircraft was underpowered.[3] However, as there was no immediate prospect for the acquisition of more powerful engines, the Saab 18 was ordered into production in both bomber (B 18A) and reconnaissance (S 18A) versio