There was a time when four-engined airliners were the norm in commercial air travel. From their roots laid in the world’s first passenger jet, aircraft manufacturers were quick to embrace the concept and readily implemented it across multiple aircraft of the ‘Jet Age’. 

Why use four engines?

To fully answer the question of why even use four engines in the first place, we must explore its origins. It was the legendary De Havilland Comet -world’s first commercial jet- that laid the groundwork for aircraft harbouring four engines. Many design flaws hindered its commercial success, allowing its competitors to capitalize on the shortcomings. The result was the emergence of the Boeing 707 and DC-8; both dominated the Jet Age and advanced the case for commercial quadjets. 

Aerospace manufacturers adopted the quadjet design from the get-go because of their compelling range. However, high fuel consumption by individual turbojet engines meant that short-to-medium haul flights weren’t economically viable.

To best illustrate the usefulness and eventual decline of the quadjets, we will revisit the story of two of the more popular ones, each meeting a fate different from the other. The iconic Boeing 747 and the exemplary Airbus A380. 

Queen of the Skies – Boeing 747

Long before any traces of the Airbus A380 surfaced, Boeing had already delivered its first jumbo quadjet, whose initial variant could carry up to 366 passengers. No commercial airliner at the time could compete with its sheer size. 

The noteworthy aspect of the 747 was that Boeing built the aircraft to fit two shoes. Not only was it a passenger jumbo jet, but it could also assume the role of a freighter if need be. This decision was largely in part of Boeing’s fears that supersonic flight would dominate air travel of the future. 

Thankfully for Boeing, this experiment paid off as the 747 still finds use as both freighter and passenger jet in many airlines today.

Superjumbo – Airbus A380

The relatively new mammoth airliner, the A380 turned 15 yesterday and is sadly nearing its demise as production halts in 2021. Though the A380 found success with its biggest operator, Emirates, Airbus failed to collect orders from other airline giants in time. A major reason for this success was the Dubai International airport. Over there, the A380 could finally do what Airbus built it for. It became Emirates’ main workhorse for lengthy transcontinental routes, transporting 525 passengers on a typical flight.

With declining orders from Emirates, Airbus finally retired the superjumbo in 2019; suffering a $25bn dollar loss in the entire A380 episode.

Decline of Four-Engined Airliners

Advancements in aircraft technology meant that jet engines became vastly more efficient and could travel a significantly greater distance than their primitive forms. The entire purpose of the quadjet was to fly long-haul routes. Now their twinjet counterparts could accomplish the same goal with almost the same number of passengers and lesser fuel. 

Additionally, Boeing and Airbus both designed their quadjets to operate within the hub-and-spoke framework. But this system disintegrated into the now dominant point-to-point model because of deregulations and better coordination between spoke cities. This means that rather than operating long-haul routes with the heavy four-engined jets, airlines preferred flying between airports with smaller and more efficient twin-jets. They also avoid paying the high operational and maintenance costs involved in keeping the quadjets in their fleet. 

As the world gravitates towards aircraft designed with a focus on optimum efficiency, a lower carbon footprint and higher fuel economy; the four-engined airliner’s survival is uncertain. Cargo airlines and militaries will, however, continue using them.

No, they won’t disappear from the skies anytime soon, but they will become a rare sight, eventually.

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