Eurocopter EC135 with the Pratt & Whitney engine are designated as P1 or P2 (with higher rated version), while the Turbomeca variant is the T1 or T2 (the latter with the Arrius 2B2). Many options have been certified, like thermal imaging cameras, searchlights, rescue hoists and EMS kits. High-quality air conditioning systems and VIP interior finishing are also available. 

The military version is named EC635, is perfectly adapted for military missions such as troop and/or load transports, training, reconnaissance and SAR missions. The EC635 gives you a choice of twin engine models-each featuring a Full Authority Digital Electronic Control (FADEC) system for the state-of-the-art power management. From startup to shutdown, the FADEC system provides optimized performance, safety and fuel efficiency. Portugal ordered the EC635 in 1997, but the order placed back in 1999 has been cancelled on August 14, 2002 due in part to delivery delays and certification. Returned to Eurocopter Germany and onward sold to RJAF - Royal Jordanian Air Force, Amman, Jordan

A technology demonstrator flew for the first time on October 15 1988, powered by two Allison 205-C20R engines. A second Bo 108 followed on June 5 1991, this time with two Turboméca TM319-1b Arrius engines. Both these machines had a conventional tail rotor.

In late 1992, the design was revised with the introduction of the Fenestron and some changes in the fuselage to enlarge the cabin for up to seven seats.

Two pre-production prototypes were built. The flew on February 15 and April 16 1994, testing the Arrius 2B and Pratt & Whitney Canada PW206B engines. A third helicopter followed on November 28 1994. 

From September 2002, the Arrius 2B2 was available; it features improved one engine inoperative power. Originally deliveries should have started in July 2002. 

The 400th (April 2005) EC135 light twin from the Eurocopter production line has been handed over to Transportes Aéreos Pegaso in Mexico City.