 In 1978, it had a specific cockpit and a T-tail, the wing had an area of 312ft² (29m²) and an aspect ratio of 8.94, the ER version targeted a MTOW of 18,300 lb (8,30 1kg) and an empty weight of 9,400 lb (4,264 kg).Assembly of the first production aircraft began in January 1979 and the first prototype made its maiden flight in May.The second prototype first flew in April 1980.