The development of a commercial aircraft is an incredibly difficult, expensive and long process. Because of this, not all designs make it into production.
Here’s five examples of aircraft that never made it into commercial service:
1. McDonnell Douglas MD-12
In the early 1990s McDonnell Douglas set about developing stretched versions of the MD-11 trijet, named MD-12X. The design eventually grew into a much larger MD-12 with four engines and two passenger decks extending the full length of the fuselage.
Unveiled in 1992, the design was similar to that of the Airbus A3XX which eventually became the Airbus A380.
The first flight was due to take place in 1995, with deliveries beginning in 1997. Despite initial excitement, no orders were placed, and the project was cancelled after key partner, Taiwan Aerospace left the project.
2. Boeing 2707 SST
The Boeing 2707 was the first supersonic transport project. After winning a government-funded bid to build an American SST, Boeing began development in the 1960s shortly after the European-built Concorde project was launched.
Boeing predicted that if the go-ahead was given, construction of prototypes would begin in early 1967 and the first flight could be made in 1970.
By October 1969, there were 122 delivery positions for Boeing SSTs by 26 airline customers including Alitalia, Delta Air Lines, Iberia and KLM.
Concerns about the environmental impact of operating the aircraft became increasingly vocal by 1970.
By 1971, despite strong support from President Richard Nixon, the US Senate rejected further funding for the project. The US House of Representatives also voted to end the SST funding on May 20, 1971.
At the time, there were 115 unfilled orders by 25 airlines, while Concorde had 74 orders from 16 customers. The two prototypes were never completed.
3. Fairchild Dornier 728 family
The Fairchild Dornier 728/928 family of aircraft were a series of jet-powered regional airliners developed by German-American aviation group Fairchild Dornier.
The two aircraft were projected to offer seating for between 50 and 110 passengers, complementing the existing 328JET series.
This type made it all the way through to the full-scale prototype stage before the company declared bankruptcy.
On March 21, 2002, the rollout of the first 728 took place – the maiden flight was due to take place during the summer of that year, with deliveries expected to begin in 2003.
Just under a month after the unveiling, on April 2, 2002, the company was rendered insolvent and forced to declare bankruptcy.
4. Avro Canada C102 Jetliner
The Avro Canada C102 Jetliner was a Canadian medium-range jet-powered aircraft built by Avro Canada in the 1940s.
The C102 made it all the way through to a flyable prototype before its cancelation in 1951.
Continued delays in Avro Canada’s all-weather interceptor project, the CF-100 Canuck, led to an order to stop working on the commercial jetliner.
The aircraft was later used as an aerial photo platform for the CF100 project but was cut up in December 1956.
5. Sukhoi KR-860
Revealed at the 2000 Paris Air Show, the Sukhoi KR-860 was a double deck, widebody superjumbo proposed by Russian aerospace company, Sukhoi.
The design had a maximum take-off weight of 650 tonnes, a payload of around 300 tonnes.
The main deck was planned to have 12-abreast seating with three aisles, while the upper deck was proposed to have nine-abreast seating with two aisles.
It was intended to carry between 860 and 1000 passengers and was designed to compete with Airbus’ newly announced A380.
The project did not get any further than the stage of marketing models.