McDonnell Douglas C-17 Globemaster III

In the late 1970s the US Air Force faced a twofold problem. Its strategic airlift fleet relied on the Lockheed C-141 Starlifter, an ageing four-jet transport limited by the diameter of its fuselage, and on the C-5 Galaxy, huge but costly to operate and demanding on runways. Tactical airlift, meanwhile, fell to the C-130 Hercules turboprop, which could use rough strips but lacked the hold and the range to move an armoured unit across an ocean. No aircraft could carry outsize cargo from the United States straight to a short runway near the front without transloading on the way.

The direct precedent was the AMST (Advanced Medium STOL Transport) competition, in which Boeing offered the YC-14 and McDonnell Douglas the YC-15. Both prototypes showed that a jet transport could take off and land in very short distances by using engine exhaust to boost the lift of the wing, but the programme was cancelled without series production. The technical lesson, however, was not lost.

In November 1979 the USAF launched the C-X programme to develop a transport larger than the AMST, with enough range to reinforce strategic airlift. Lockheed submitted a C-5-based design and an enlarged C-141; Boeing, a development of its YC-14; and McDonnell Douglas, a new aircraft that scaled up the configuration of the YC-15. On 28 August 1981 the McDonnell Douglas proposal was selected and designated C-17.

The full-scale development contract was not awarded until December 1985, and manufacture of the first aircraft followed at the McDonnell Douglas plant in Long Beach, California. The USAF set a requirement for 210 aircraft, a figure that would not last: in April 1990 Secretary of Defense Dick Cheney cut it to 120.

The first C-17 took off from Long Beach on 15 September 1991 and landed at Edwards Air Force Base, roughly a year behind schedule. The problems had only just begun. The programme was running over budget, production was late, and the wing failed its static structural test: after some 100 million dollars had been spent on a redesign, it broke again in September 1993 at 145 per cent of limit load, short of the required margin.

The Department of Defense responded with an ultimatum: the contractor had two years to solve its production and cost problems, or the contract would be terminated after delivery of the 40th aircraft. In parallel, a programme was set up to study buying commercial freighters as an alternative or a supplement. Accepting those terms cost McDonnell Douglas a loss of nearly 1.5 billion dollars on the development phase, but the company sorted out the line and the programme survived: in 1996 the Department of Defense ordered another 80 aircraft, for a total of 120.

Meanwhile, in early 1993 the aircraft had been named Globemaster III, in tribute to two Douglas freighters, the C-74 Globemaster and the C-124 Globemaster II. The first production aircraft arrived at Charleston Air Force Base, South Carolina, on 14 July 1993, and the C-17 formally entered service on 17 January 1995.

The C-17 is a high-wing monoplane with a T-tail, four engines in pods under the wing and a large rear ramp. Its supercritical wing gives it a cruise speed of around Mach 0.74. The key to its short take-off and landing performance lies in the externally blown flaps inherited from the YC-15: engine exhaust is directed over the lowered flaps and increases lift at low speed, allowing steep, slow approaches with a heavy load.

It is powered by four Pratt & Whitney F117-PW-100 turbofans, the military version of the PW2040 used on the Boeing 757. Their thrust reversers direct the exhaust upwards and forwards, which reduces the risk of the engines ingesting runway debris and provides enough force for the aircraft to taxi backwards on ramps and narrow taxiways, a manoeuvre most large jets cannot perform.

The flight deck is designed for two pilots with head-up displays, and the basic crew is completed by a single loadmaster, who handles the hold. The hold can take one M1 Abrams tank, two Bradley vehicles or three Strykers, up to 18 standard 463L pallets, 102 paratroopers or 134 seated troops, or an aeromedical evacuation layout with 36 litters. The aircraft can operate from runways as short as 3,500 ft and as narrow as 90 ft.

Since entering service the C-17 has taken part in almost every American operation. It played a key logistical role in Afghanistan and Iraq. On 26 March 2003, fifteen C-17s dropped 1,000 paratroopers of the 173rd Airborne Brigade at night over Bashur in northern Iraq: the largest combat airdrop since the invasion of Panama in 1989.

Since 1999 the aircraft has flown to Antarctica every season on Operation Deep Freeze, supporting the US Antarctic programme and replacing the C-141s used before. It has also delivered humanitarian aid after disasters such as the 2010 Haiti earthquake. In August 2021, during the evacuation of Kabul airport, a C-17 of the 816th Expeditionary Airlift Squadron carried 823 Afghan civilians on a single flight, a record for the type.

The USAF eventually decided to cap its fleet at 223 aircraft and received the last one on 12 September 2013. Aircraft from the later batches carry additional fuel tanks in the centre wing section, and Boeing informally calls them C-17 ER because of their greater range.

Among foreign customers, the Royal Air Force operates eight aircraft from Brize Norton. Australia followed with eight, and Canada operates five under the designation CC-177; in April 2010 one of them landed for the first time at Alert, the most northerly airfield in the world, and in 2013 Canadian aircraft flew an air bridge to the Philippines after Typhoon Haiyan.

Qatar received its first C-17 on 11 August 2009, and the United Arab Emirates and Kuwait joined the list. India expressed interest in 2010 and became the largest foreign customer, with 11 aircraft based at Hindon. In Europe, a group of NATO members and partners signed a letter of intent at the 2006 Farnborough Airshow to share aircraft through the Strategic Airlift Capability programme: its Heavy Airlift Wing operates three C-17s from Pápa Air Base in Hungary.

After the 1997 merger with McDonnell Douglas, Boeing took over the programme. With international sales slowing, partly because of competition from the Airbus A400M, Boeing announced the closure of the line: in October 2014 the main wing spar of the 279th and last aircraft was completed; it was finished at Long Beach and flown in November 2015, after which the California plant closed. That final aircraft went to India, bringing its fleet to 11 C-17s.

There was no direct successor. A civil version for the airlines of the Civil Reserve Air Fleet (BC-17X) and a tactical C-17B with double-slotted flaps, an extra main landing gear and more powerful engines were studied, but neither left the drawing board. More than three decades after its first flight, the Globemaster III remains the freighter that allows the United States and its allies to move heavy equipment anywhere in the world and set it down on short runways close to where it is needed, and it is a regular at air shows, where its short take-offs and tight turns belie its size.