 The Avro 608 Hawk was a proposed two-seater fighter variant of the Antelope, which was planned to be powered by a Bristol Jupiter radial engine.Although construction of a prototype began, it was incomplete when it was redesigned with a 540 hp (400 kW) Armstrong Siddeley Panther engine as the Avro 622.Following interest by Canadian Airways, who had a possible requirement for a mail plane, Roy Chadwick again redesigned the incomplete prototype to the Avro 627 Mailplane .