The Blenheim production program saw several shifts in requirements and in capacity. A modified Blenheim design, given the name "Bolingbroke", was manufactured under licence in Canada by Fairchild Aircraft. The Bolingbroke, which had been developed in response to Air Ministry Specification G.24/35 to procure a coastal reconnaissance/light bomber as a replacement for the Avro Anson, had substantial improvements that would serve as the basis for improved variants of the Blenheim. According to aviation author James D. Oughton, both the navigator's station and range limitations of the Blenheim Mk I had been subject to considerable criticism, thus an improved model of the aircraft was desired in order to rectify these shortcomings. On 24 September 1937, an experimental Blenheim Mk I, modified with an extended forward fuselage beyond its original stepless cockpit, smooth-fronted nose enclosure, made its first flight from Filton.