The Militky MB-E1 was a modified version of the HB-3 airframe and the first manned electric aircraft to make a successful flight. The first flight took place on 23 October 1973. The plane only flew for 12 minutes though, with a maximum altitude of 380 meter. It used the 8-10 kW Bosch KM77 electromotor. The use of Ni-Cd batteries decreased capacity and significantly increased weight compared to Lithium-Ion technology.