01/31/2011. Remarks by Claudio Delfini: "The first post-war aircraft designed in Poland with a Polish engine, the Bies (Fiend) was designed by a team led by Tadeusz Soltyka at the Instytut Lotnictwa (Aviation Institute) of Warsaw in 1952. It was designed for basic flight training, as well as for fighter pilot training and the initial test flight of the Bies took place on July 23, 1955.

After three years of development, production of the Bies started in the Mielec factory where a total of 250 units were produced. The Bies was delivered to the Officers Training School (OTS) as well as to various units of the Polish AF, and to the Polish Naval Air Arm. From the mid-1960s the Bies was gradually withdrawn, although a number of aircraft were used in the liaisons role through the 1970s."