The Eurocopter H135 started development prior to the formation of that company, by MBB under the designation Bo 108 in the 1970s

The Bo-108 was the intended successor of the highly successful Bo-105. It had a more steamlined pod, digital engine controls and more powerful engines. When MBB became part of Eurocopter a fenestron tail rotor was introduced and the type was rebranded EC-135.

Second prototype from 1991 of predecessor of Eurocopter EC-135. Both prototypes were used as technology demonstrators and unlike later production aircraft flew with conventional tail rotors.