A cargo aircraft (also known as freight aircraft, freighter, airlifter or cargo jet) is a fixed-wing aircraft that is designed or converted for the carriage of cargo rather than passengers. Such aircraft usually do not incorporate passenger amenities and generally feature one or more large doors for loading cargo. Freighters may be operated by civil passenger or cargo airlines, by private individuals or by the armed forces of individual countries. Aircraft designed for cargo flight usually have features that distinguish them from conventional passenger aircraft: a wide/tall fuselage cross-section, a high-wing to allow the cargo area to sit near the ground, numerous wheels to allow it to land at unprepared locations, and a high-mounted tail to allow cargo to be driven directly into and off the aircraft. By 2015, dedicated freighters represent 43% of the 700 billion ATK (available tonne-kilometer) capacity, while 57% is carried in airliner's cargo holds. Also in 2015, Boeing forecast belly freight to rise to 63% while specialised cargoes would represent 37% of a 1,200 billion ATKs in 2035. The Cargo Facts Consulting firm forecasts that the global freighter fleet will rise from 1,782 to 2,920 cargo aircraft from 2019 to 2039. History Aircraft were put to use carrying cargo in the form of air mail as early as 1911. Although the earliest aircraft were not designed primarily as cargo carriers, by the mid-1920s aircraft manufacturers were designing and building dedicated cargo aircraft. In the UK during the early 1920s, the need was recognized for a freighter aircraft to transport troops and material quickly to pacify tribal revolts in the newly occupied territories of the Middle East. The Vickers Vernon, a development of the Vickers Vimy Commercial, entered service with the Royal Air Force as the first dedicated troop transport in 1921. In February 1923 this was put to use by the RAF's Iraq Command who flew nearly 500 Sikh troops from Kingarban to Kirkuk in the first ever strategic airlift of troops. Vickers Victorias played an important part in the Kabul Airlift of November 1928 – February 1929, when they evacuated diplomatic staff and their dependents together with members of the Afghan royal family endangered by a civil war. The Victorias also helped to pioneer air routes for Imperial Airways' Handley Page HP.42 airliners. The World War II German design, the Arado Ar 232 was the first purpose-built cargo aircraft. The Ar 232 was intended