In June 1935, owing to the urgent need to replace biplane heavy bombers then in service with the RAF, a verbal agreement was formed to produce an initial 80 aircraft, 40 being of an early "Whitley Mk I" standard and the other 40 being more advanced "Whitley Mk IIs". Production was initially at three factories in Coventry; fuselages and detailed components were fabricated at Whitley Abbey, panel-beating and much of the detailed work at the former Coventry Ordnance Works factory, while wing fabrication and final assembly took placed at Baginton Aerodrome. During 1935 and 1936, various contracts were placed for the type; the Whitley was ordered "off the drawing board" - prior to the first flights of any of the prototypes.