The AS.45 was designed in response to Air Ministry Specification T.4/39 for a single engine trainer.
It was a low wing monoplane of composite construction with a single piston engine and a tail wheel type, retractable undercarriage.
The first of two prototypes flew on 19 February 1941.
Testing showed deficiencies in both maximum speed and low speed flight characteristics.
There was no attempt to rectify these shortcomings, partly because there was no shortage of advanced trainers thanks to plentiful supplies of Masters and Harvards and partly because of the importance of Airspeed’s other products, the Horsa and Oxford.