The AgustaWestland AW139 is a 15-seat medium-sized twin-engined helicopter developed and produced by the Anglo-Italian helicopter manufacturer AgustaWestland (now part of Leonardo). It is marketed at several different roles, including VIP/corporate transport, offshore transport, fire fighting, law enforcement, search and rescue, emergency medical service, disaster relief, and maritime patrol. The AW139 was originally designed jointly by the Italian helicopter manufacturer Agusta and the American company Bell Helicopters, thus it was marketed as the Agusta-Bell AB139, but was redesignated as the AW139 after Bell withdrew from the project. In addition to AgustaWestland's manufacturing facilities in Italy and the United States, other companies are also involved in the programme, such as the Polish manufacturer PZL-Świdnik, which has produced hundreds of AW139 airframes, and HeliVert, a joint venture between AgustaWestland and Russian Helicopters, which has also established a production line inside Russia for the type. Having performed its maiden flight on 3 February 2001, the AW139 entered revenue service during 2003 and quickly proved itself to be a commercial success. Many of the AW139 customers have been in the civilian sector; large fleets have been obtained by operators such as CHC Helicopter, Gulf Helicopters, and Weststar Aviation. Its performance has enabled it to become popular amongst operators supporting the offshore oil and gas industry. A dedicated militarised model, the AW139M, was also developed by AgustaWestland; it was first procured by the Italian Air Force, other military operators include the United States Air Force, which operates the MH-139 Grey Wolf model. The Japanese business Mitsui Bussan Aerospace has obtained an exclusive distribution agreement for the AW139 in the country. Over 1,100 rotorcraft had been sold by January 2021. The AW139 has been subsequently developed into the AW149, an enlarged medium-lift military-orientated rotorcraft. Development Origins In 1997, the Italian helicopter manufacturer Agusta launched a programme to develop a replacement for the Bell Huey family of helicopters (which had been built in very large numbers by Bell Helicopter and under license by Agusta). A potential market of 900 aircraft was predicted. In 1998, Bell and Agusta entered into an agreement setting up a joint venture, Bell/Agusta Aerospace Company (BAAC), to develop two aircraft: a conventional helicopter and a tiltrotor aircraft. These became the Bell/Agusta AB139 and Bell/Agusta BA609 respectively. Bell was to be the leading partner for the development of the BA609 while Agusta would be the lead partner for the AB139; it was intended for