Airlines take a risk when operating quadjets, as the majority of them, except for planes like the BAe 146 regional jet series, are among the largest aircraft in the sky.
There’s a rich history when it comes to these aircraft that once ruled the skies. In this post, we will cover what led to the construction of quadjets and which went on to the prototype and production phases.
The Rise of Four-Engine Jetliners
Before the Jet age, airplanes were powered by piston engines. The failure rate for such machines was higher, so to avoid such problems, the most practical way for designers was to build a four-engine airliner.
Besides redundancy, early jet engines produced less thrust so that the aircraft could have more power with four engines. Subsequently, the airline can carry more passengers, heavier cargo and payloads, and, most importantly, increase performance.
Some major four-engine airliners can carry more than 500 passengers; this allows airlines to serve the busiest routes. Likewise, the carriers can distribute the operating costs and make more profits. But there were some drawbacks that lead to the decline of quad jets as we will later see.
There were 120 four-engine aircraft designed. Many went into the prototype and production phases and were used for various purposes. Some 21 quad jets are still operated by commercial airlines.
For this post, we have listed the aircraft in order of their first flights.
1. de Havilland Comet
The world’s first commercial jet airliner is de Havilland DH.106 Comet. The quad jet is designed and built by United Kingdom-based de Havilland. It was a narrowbody airliner with engines located under the wings.
The aircraft had four variants, and the company named them Comet 1,2,3,4. Comets 1 and 2 used to occupy 36-44 passengers, while Comet 3 could carry 76 passengers, and Comet 4 had 81 seats.
Comet 1 was powered by de Havilland Ghost 50 Mk1 turbojet engines. While Comet 2 got propulsion from Rolls-Royce Avon AJ.65 engines. Subsequently, Comet 3 and 4 were powered by upgraded Avon engines. As reported by popular science, the Avon-powered Comet 4 had increased takeoff performance at higher altitudes, such as Mexico City, where Mexicana de Aviacion operated it.
It was involved in various incidents and accidents due to structural failure caused by metal fatigue. Following such catastrophic losses, the company redesigned its aircraft heavily and introduced later variants. However, the sale for it never recuperated, and de Havilland only produced 114 comet aircraft, including prototypes. They closed Comet’s production in 1964, and Last Comet retired on March 14, 1997.
2. Avro Canada C102 Jetliner
Canadian airliner, Avro Canada C102 Jetliner, was a prototype built by Avro Canada in 1949. It was a medium-range four-engine airliner that commenced its first flight on August 10, 1949.
The company first used the term ‘Jetliner,’ which was taken from Jet and Airliner. This term is used widely today for commercial aircraft powered by jet engines.
Following the delay with Avro Canada’s CF-100 Canuck project, the only Canadian-designed fighter to enter mass production, the plan to mass-produce C102 Jetliner was scrapped in 1951.
The C102 was initially powered by four Rolls-Royce Derwent V centrifugal-flow turbojet engines. Later they changed them into different sets of Derwent engines.
American business magnate, record-setting pilot, engineer, film producer, and philanthropist Howard Huges ordered 30 such aircraft for its Trans World Airlines (TWA). Still, following the delay and inability to produce the plane, they rejected the offer.
3. Tupolev Tu-110
The USSR-made Tupolev Tu-110 was designed by Dmitriy S. Markov and built by Tupolev at the Kazan Aircraft Factory. The Cooker, which NATO named, was developed from a narrowbody twinjet, Tupolev Tu-104.
The first prototype made its first flight on March 11, 1957. Four Lyulka AL-7 turbojets powered it. Unfortunately, Russian manufacturers only built four such jetliners.
The production aircraft had extended-chord wings, and enlarged baggage holds. It could carry up to 100 passengers.
Tupolev decided to improve its performance by using Soloviev D-20 turbofan engines on all prototypes and named them as Tu-110Bs. However, the company received no further orders and only used the prototypes for testing. They used Tu-110 for studying the avionics, missile systems, and boundary layer control systems until the 1970s.
4. Boeing 707
American narrowbody airliner, Boeing 707, is the first jetliner developed by Boeing. It was designed from the Boeing 367-80, the sole quad jet prototype built to demonstrate the benefits of jet propulsion for commercial flying in 1954. However, Boeing 367-80 was crucial in developing 707s and KC-135 tanker aircraft.
The quad jet had its maiden flight on December 20, 1957, almost 65 years ago. It entered the service with Pan American World Airways (PA) on October 26, 1958. Although it’s not the first jetliner, due to its popularity and success, it is credited with the beginning of the Jet Age.
The Boeing 707 has more than half a dozen variants; the most significant variant, 707-320C, can carry 194 passengers. While the smallest 707-120 can occupy 174 passengers. The 707-320B and -320C were the most successful variants, as both were produced in three digits.
The jetliner ruled the 1960s and 1970s. Pratt and Whitney JT3C/D powered all its variants except the 707-420 that Rolls Royce RB Conway-12 powered.
The plane, over time, has flown with global airlines spread across six continents. To date, Boeing has produced 865 Boeing 707s variants that have served both commercial airlines and military forces across the globe.
5. Douglas DC-8
The long-range narrowbody, jetliner Douglas DC-8, was designed and built by the American Douglas Aircraft Company. It remained the biggest competitor to Boeing 707 jetliner.
The DC-8 made its first flight on May 30, 1958. Following the FAA certification, it entered into service with Delta Air Lines (DL) and United Airlines (UA) on September 18, 1959.
It got its power from Pratt & Whitney JT3C and JT4A turbojets. At the same time, the intercontinental variant DC-8-30 was powered by P&W JT4A and DC-8-40 by Rolls-Royce Conway 509 turbofan engines.
The American plane manufacturer named its variants series and subseries 10, 20, and so on till super series 70. The initial three variants had 177 seats, while the series 60 and 70 sub-variants could occupy 259 passengers.
The Douglas Aircraft Company and, later, McDonnell Douglas produced 556 DC-8 jetliners before ending production in 1972. Most recently, in January 2023, NASA replaced the DC-8 with the Ex-Japan Airlines (JL) Boeing 777-300ER.
6. Baade 152
The first jetliner developed in Germany, Baade 152, also known as Dresden 152, VL-DDR 152, or simply 152. It was designed and built by VEB Flugzeugwerke Dresden, the aircraft company in East Germany.
The aircraft was named after its chief designer and aeronautical engineer, Brunolf Baade. They developed the plane from the OKB-1 150, the Soviet Union’s jet bomber of 1948.
It made its first flight on December 4, 1958. The German company developed three aircraft; two were used as flight test prototypes, and one was entirely manufactured but never flew. Several Baade 152 were in production but were canceled following problems with fuel supply with prototypes.
Four indigenously-developed Pirna 014 turbojet engines powered it. The aircraft had various seating configurations, and the highest was 72 passengers capacity. By mid-1961, the company scrapped all the planes.
7. Convair 880
The Convair 880 was an American Jetliner built by Convair, a division of General Dynamics, to compete with the Boeing 707 and Douglas DC-8. It was a small narrowbody jetliner initially named Skylark, then Golden Arrow, later Convair 600, and finally getting Convair 880.
The aircraft commenced its maiden flight on January 27, 1959. It entered into the service with DL on May 1960. It had two variants powered by four General Electric CJ-805-3/3B turbojet engines. Both models could carry 110 passengers. It flew with close to 50 airlines at that time, but it failed to receive significant orders from them.
It was unattractive to airlines due to its five abreast seating configurations and failed to compete with Boeing 707s and later with 720s. The parent company, General Dynamics, lost millions of dollars in this project. Over the three years of the production line, they produced only 65 such aircraft.
The company then produced the majority-modified model of 880 and named it Convair 990 Coronado, which we will see at number 9.
8. Boeing 720
Another American plane manufactured by Boeing Commercial Airplanes, the Boeing 720, a derivative of the Boeing 707, was a narrowbody announced in 1957. Boeing developed it for shorter routes and could take off and land on shorter runways.
The Boeing 720 first took to the skies on November 23, 1959. The quad jet made its debut with UA on July 5, 1960. The company spent significantly less to develop 720s as it was modified 707, and despite having fewer sales than 707, it was profitable.
It is the only airliner produced that does not follow the Boeing 7×7 scheme. It was powered by four Pratt & Whitney JT3C/3D turbojet engines. It had two variants, and both had the capacity to occupy 156 passengers in one class configuration.
Following the development of new variants, Boeing stopped the 720s production in 1967 and produced 154 such aircraft. The 727s, the most-produced trijet aircraft in the world, succeeded the 720s.
9. Convair 990 Coronado
Another American single-aisle jetliner, the Convair 990 Coronado was designed and manufactured by Convair. It was developed by stretching the Convair 880 as American Airlines (AA) requested.
Convair 990 Coronado made its first flight on January 24, 1961. It came into service in 1962 and was mainly operated by AA, Spantax (BX), and Swissair (SR). It was powered by a unique rear fan rotor designed, uprated General Electric CJ-805-23s turbofan engines.
The aircraft was 25–35 mph (40–56 km/h) faster in the cruise phase than its existing competitors. It had the capacity to occupy up to 149 passengers.
Like its predecessor, Convair 880s, the 990s didn’t receive many orders, and the General Dynamics aircraft division only produced 37 such aircraft. The aircraft commercially retired from service on September 1987 and in 1994 by NASA.
10. Vickers VC10
The long-range narrowbody airliner, Vickers VC10, was designed and built by Vickers-Armstrongs (Aircraft) Ltd. The British manufacturer created VC10 considering shorter runways and the hot weather of Africa.
The Vickers VC10 made its first flight on June 29, 1962, at Brooklands, Surrey. The aircraft was introduced on April 29, 1964, with BOAC.
A subsonic jet airliner, VC10 achieved the quickest Atlantic crossing with 5 hours and 1 minute, setting a record that stood for 41 years. However, in February 2020, during Storm Ciara, a British Airways (BA) Boeing 747 surpassed the previous record with 4 hours and 56 minutes.
It got its propulsion from four Rolls-Royce Conway Mk 301 turbofan engines. It had various commercial and military variants and could carry over 150 passengers.
Despite having various specialties, the company only produced 54 of this type. The aircraft retired on September 20, 2013, with UK’s Royal Air Force.
11. Ilyushin Il-62
The Ilyushin Il-62 is a long-range single-aisle jetliner designed and built by Soviet Ilyushin at the Kazan factory. It was considered one of the four pioneering long-range airliners; others were Boeing 707, DC-8, and VC10.
The aircraft had its maiden flight on January 3, 1963. Ilyushin Il-62 came into service on September 15, 1967, while Il-62M on March 9, 1974. With a capacity for up to 200 passengers and crew, it was the longest jetliner among others when it flew for the first time in 1963.
Four Soloviev D-30KU turbofan engines power the Il-62 and its variants. The aircraft was successful, and the company manufactured 295 aircraft, including prototypes and both standard variants.
Air Koryo, Aeroflot (SU), Russian VIP transport, and LOT Polish Airlines (LO) are/were its primary operators. Some government officials still operate the Il-62. The company, however, stopped its production almost 23 years ago, in 1995.
12. Tupolev Tu-144
At number 12, we have the world’s first supersonic airliner, Tupolev Tu-144, designed and built by USSR Tupolev. NATO gave it the code name ‘Charger.’ It was designed by the veteran Soviet plane designer Andrey N. Tupolev and his son Alexey.
The Tu-144 prototype made its first flight from Zhukovsky International Airport (ZIA) on December 31, 1968, two months before the Anglo-French Concorde. The Voronezh Aircraft Production Association in Voronezh manufactured it.
The Russian supersonic jet first entered into passenger service with SU on November 1, 1977. SU flew the TU-144 between Moscow and Alma-Ata. It was powered by extreme fuel feast four Kolesov RD-36-51 turbojets developed at OKB-36 and built at the Rybinsk Motor-Building Plant.
The supersonic airliner had the capacity to occupy 150 passengers. Over its operational years, it made more than 100 flights, and 55 of them had passengers on board. It used to fly at an average service altitude of 16,000 meters (52,000 ft). On May 26, 1970, it became the first supersonic airliner to exceed Mach 2, i.e., travel two times faster than the speed of sound.
However, Tu-144’s suitability for frequent use was limited by various factors such as reliability and developmental challenges, the aftermath of the 1973 Paris Air Show Tu-144 crash, and the increasing fuel cost. Due to this, the Soviet Union decided to stop its production in 1983.
SU, the USSR aviation ministry, and NASA primarily operated the aircraft. It was finally retired from the world on June 26, 1999, and some of them went to storage for the showcase.
13. Boeing 747
Between Tupolev Tu-144 and Concorde came the queen of skies, the Boeing 747, the world’s first widebody airliner designed and built by Boeing in the late 1960s.
Joseph Frederick Sutter, popularly known as Joe Shutter, was an American engineer; he managed the design team for the Boeing 747, working under Malcolm T. Stamper, who was in charge of the 747 projects at Boeing Commercial Airplanes.
The aircraft rolled out of Everett Plant, the world’s largest factory by Volume, on September 30, 1968. Jumbojet flew for the first time on February 9, 1969. It entered into service with Pan Am (PA) in the presence of First Lady of the United States Pat Nixon on January 15, 1970, at Washington Dulles International Airport (IAD).
Boeing developed dozens of variants of the 747s. Different options of engines, such as Pratt & Whitney JT9D, Rolls-Royce RB211, or General Electric CF6, powered the initial models. However, the later variants are powered by P&W 4000 and 747-8 by GEnx-2B67.
From a smaller model, 747SP carried 400 passengers, to the 747-400 had exit limits of 660 passengers. The 747 pioneered the golden age of commercial air travel of the 1960s.
The semi-double-decker was/is primarily operated by Atlas Air (5Y), Lufthansa (LH), Cargolux (CV), and UPS Airlines (5X). Boeing produced 1,574 747s, including prototypes, and delivered the last 747 to 5Y.
There are many facts regarding the 747, but one standout fact is that Boeing was king in the commercial quad jet market with the Queen of the Skies for many years. Airbus would launch the A340 in 1993 and the A380 in 2005.
Aérospatiale/BAC Concorde was the narrowbody supersonic airliner designed and developed jointly by the British Aircraft Corporation (BAC) and French Sud Aviation (later Aérospatiale).
The Supersonic aircraft program began in 1954 as a treaty between British and France, and it cost an estimated £70m (£1.39bn in 2021) to them. However, the program underwent massive expense overruns and delays, ultimately costing between £1.5 and £2.1bn in 1976 (£9.44bn-13.2bn in 2021).
Concorde first flew on March 9, 1969, from Toulouse, France. A supersonic airliner entered into service with Air France (AF) and BOAC (BA) on January 21, 1976, seven years after its first flight.
Manufacturers predicted the market size of 350 such airliners and received option orders for up to 100 Concorde from many global airlines. However, they produced only 20 Concordes, including 6 non-commercial ones, as various airlines questioned its viability for commercial air travel. The airlines canceled the orders, and only AF and BOAC flew them.
The “aviation icon,” as described by Flight International magazine, was powered by four Rolls-Royce/Snecma Olympus 593 Mk 610 turbojets with an afterburner. It had the capacity to occupy 92 up to 120 passengers.
Various factors contributed to Concorde’s decline, including high fuel consumption, sonic boom, and fatal crashes. The Concorde made its last flight to Filton, Bristol, UK, on November 21, 2003.
15. Ilyushin Il-86
The USSR’s first widebody airliner, Ilyushin Il-86, is a short to mid-range aircraft developed and experimented with by the Ilyushin design bureau in the 1970s. Voronezh Aircraft Production Association built it.
As there were larger US and European aircraft, the USSR wanted more than 200 seaters to compete with them. Many ideas were suggested, including 724-seater aircraft, double-decker, two fuselage side by side, and the civilianized version of the Ilyushin Il-76.
However, after evaluating various possibilities, Illyushin decided to go ahead with 350 seater variant. It was powered by four Kuznetsov NK-86 low bypass turbofan engines, an upgraded version of NK-8.
The aircraft made its first flight on December 22, 1976. It entered into operations on an inaugural service between Moscow and Tashkent on December 26, 1980. The SU, Siberian Airlines (S7), Kras Air (7B), and Donavia (D9) were its primary operators.
Despite many aircraft advancements, it didn’t receive much attention and was operated by Russian airlines, and only three Il-86 were exported to others. Following this, Illyushin manufactured 106 Il-86 jetliners until 1991. By the end of 2020, there were three active Il-86, and that too in limited service.
16. Shanghai Y-10
The first Chinese quad jet, the Shanghai Y-10, was a narrowbody airliner manufactured by the Shanghai Aircraft Manufacturing Factory. It was designed with reference from Boeing 707 and according to FAA standards.
Earlier in the 1970s, the Shanghai Aircraft Research Institute named Aircraft 708. The plane was designed to study future aircraft development and purely served as a demonstrator. It flew for the first time on September 26, 1980.
However, the project was controversial from the beginning due to politics. Reuters reported the Chinese government’s statement, “After creating this sort of admiringly intricate technology, one could no longer consider China a backward nation.”
The aircraft was powered by four Pratt & Whitney JT3D-3B turbofan engines, the same engine type that powered the Boeing 707 and Douglas DC-8. All three prototypes had different types of testing roles, first used for static testing, second for flight testing, and last for fatigue tests.
Later some reports suggested it was copied from Boeing 707 using reverse engineering, while some stated it was more similar to the 720s. However, both Y-10 manufacturers and Boeing denied the allegations. Today, the Commercial Aircraft Corporation of China, Ltd.’s (COMAC) success results from earlier research on aircraft development.
17. BAe 146
The British Aerospace 146 acronym of BAe 146 is the short-range regional jetliner developed by the BAE system, earlier known as British Aerospace. The company later formed Avro International Aerospace to consolidate production of the BAe146 at Woodford Aerodrome.
Avro produced a new model of BAe 146, also named Avro RJ, which had three variants RJ-70, RJ-85, and RJ-100 variants. Similar to its predecessor, which had three civilian models and two military variants.
The BAe 146/ Avro RJ prototype made its maiden flight on September 3, 1981, and was introduced to service in May 1983. Mahan Air (W5), National Jet Express (NC), and Pionair Australia (PH) are among the significant operators of aircraft.
The BAe 146 variants are powered by four Lycoming ALF 502R-5 geared turbofan engines, and the Avro RJ models are by four Honeywell LF 507-1F geared turbofan engines. The three major variants had capacities ranging from 70 to 112 seats.
The aircraft has been operated by various airlines across the world. However, the airline stopped its production in 1991 and manufactured 394 aircraft. The Avro RJ100 has been used as a testbed for Airbus/Rolls-Royce/Siemens E-Fan X, a hybrid electric aircraft.
18. Antonov An-124
The Antonov An-124 has a passenger variant, despite being widely recognized as a heavy transport freighter. The type is a large strategic airlift designed by the Antonov design bureau in the Ukrainian SSR, then part of the Soviet Union (USSR).
The commercial air transport variant was known as An-124-100. It can carry up to 88 passengers in the upper aft fuselage, or the hold can take an additional 350 pax on a palletized seating system.
Antonov An 124 Ruslan made its first flight on December 24, 1982, and was introduced to service in 1986. The Russian freight mover is powered by four high-bypass Progress D-18T turbofan engines. The same engine was used to power the world’s largest cargo aircraft, An-125 Mirya, as it was an enlarged version developed from An-124.
However, the aircraft’s freight model is much more significant and has been primarily operated by Russian Air Force and Volga-Dnepr Airlines (VI). At the same time, Antonov also has a cargo airline, Antonov Airlines (ADB), and operates An-124 aircraft.
The company, to date, has produced 55 such aircraft before ending production in 2004. By 2019, nearly half of them still remain active in commercial service.
19. Ilyushin Il-96
Another Russian jetliner, Ilyushin Il-96, is a long-range twin-aisle designed by Ilyushin and manufactured by the Voronezh Aircraft Production Association in Russia.
The aircraft made its maiden flight on September 28, 1988. It entered into service with SU on December 29, 1992. The plane was developed from Il-86 and has been in limited production since 1992.
The aircraft has multiple variants, and the passenger variant Il-96-300 is powered by Aviadvigatel PS-90, Il-96M is by Pratt & Whitney PW2000, and Il-96-400 by Aviadvigatel PS-90A1. The Il-96-300 can occupy 300 passengers, while Il-96-400 carries 436 passengers in a single-class configuration.
Despite having nearly a dozen variants, it hasn’t succeeded, and the company has produced only 30 Il-96 models.
20. Airbus A340
European-made long-range widebody airliner, Airbus A340, is the first quad jet produced by Airbus. It is developed from Airbus’ first airliner, the A300, and has a similar fuselage structure.
Airbus A340 made its first flight on October 25, 1999, almost 30 years ago. It entered commercial service with LH and AF on March 15, 1993. Today the LH, W5, LX, and Edelweiss Air (WK) are major operators of the A340 airliner.
The jetliner has four variants and can carry more than 350 passengers in exit limits on all its models. The early variants A340-200/300 get their power from CFM International CFM56-5C while A340-500/600 by Rolls-Royce Trent 500 high bypass turbofan engines.
A340-600 is one of the longest jetliners. Airbus produced 380 variants of A340s before closing the assembly line in 2012. As of December 2022, there were more than 200 A340s in commercial service with 45 global operators. It is among the last four-engine airliner.
21. Airbus A380
The world’s largest passenger airliner, Airbus A380, was designed and built by Airbus. The aircraft is the first and most recent quad jetliner of the 21st century.
The world’s only double-decker aircraft made its first flight on April 27, 2005. It was introduced to the world in the Singapore Airlines (SQ) livery on October 27, 2007, almost 16 years ago.
The company started working secretly in mid-1988 to produce an ultra-high-capacity airliner (UHCA) to compete with the Boeing 747s and end its dominance. Following various considerations, partnerships, and n number of hours, Airbus finally chose a double-decker design and built A380, which has three variants based on engine types.
The A380-841 is powered by four Rolls Royce Trent 970-84/970B-84, A380-842 by RR Trent 972-84/972B-84, and A380-861 by Engine Alliance GP7270. In a typical configuration, it has 575 seats and can carry 853 passengers.
Airbus has produced 254, nearly six times lesser than its nearest competitor, Boeing 747 (1,574). Emirates (EK), as of March 2023, operates close to 119 A380s, slightly less than the total produced until 2021. It is one of the safest aircraft in the world. Moreover, only a dozen of operator currently operates A380s. However, various factors led to the gradual decline of four-engine jetliners.
The Rise of the Modern Twinjet
By the 1980s, an increase in jet engine performance led to the introduction of the ETOPS rating for twinjets. This means airlines no longer need the redundancy provided by quad jets.
The quad jets consume more fuel and are costlier to maintain than the twin jets. Also, the introduction of larger twinjets such as Boeing 777, 767, and later Boeing 787s and Airbus A350s ensured that airlines could fly long haul and carry more passengers with just two-engine jetliners.
However, the plane manufacturers developed all types of quad jets ranging from A380s and Jumbo jets which carried 500 passengers, long to medium range 300 seater airliners to short-range regional BAe 146 aircraft.
Ultimately, by the 21st century, the only advantage for four-engine airliners is their ability to occupy more passengers. The airlines want an aircraft that is flexible and, at the same time, economical to operate on both medium and long-range routes, and modern twinjets deliver it.
In short, higher fuel consumption, lesser demands on specific routes, more advanced engines, high maintenance costs, and the development of high-capacity twinjets led to the steep decline of quad jets.
Once recognized as the pioneer of the jet age, the quad jet is today a thing of the past, at least for passenger travel. The four-engine airliners are seen less and less in the skies and no such aircraft is in production. Additionally, operators are retiring their four-engine aircraft fleets and replenishing them with modern aircraft.
While it is unlikely that we will soon see the production of new quad jets, we might see short-range four-engine electric and hydrogen-powered planes.
Feature Image: N401PW was pictured during its maiden flight in 1988. Photo: Delta Air Lines