Hawker 400A was developed from scratch. This is a high class jet. It was promoted as the top model of a private business jet. In 1990, the car has undergone a number of improvements. They increased the flight range, take-off weight, and also made the cabin more spacious and comfortable. The interior was luxurious. The designers suggested creating an all-glass floor. The modernization affected aerodynamic and mechanical systems. The original developer was Mitsubishi MU-300 Diamond. Then the rights were bought by the company Raytheon.