Double-decker planes are going extinct as Airbus and Boeing discontinue their largest models. Here's why airlines are abandoning 4-engine jets.

• The Airbus A380 and Boeing 747 are quickly being phased out by some airlines as the coronavirus pandemic has eliminated the dwindling demand for the four-engine planes.
• Boeing is ending the 747 production line in 2022 while Airbus just delivered its last A380 fuselage to the assembly line in France in June.
• High operating costs and efficient twin-engine alternatives marred orders for both planes in the 2010s as the manufacturers promised jets that could fly further for cheaper.

It's the end of an era for four-engined planes.

Boeing is stopping production of its famed 747 aircraft by 2023 and Airbus just trucked its last A380 fuselage through France in June as it prepares to shut down the line in 2021 after less than two decades of production. Both were a casualty of weak demand from the airlines they faithfully served amid a crippling pandemic, though their popularity began to wane long before the first COVID-19 case was reported.

The once-long-haul leaders are now being put out to pasture and the coronavirus pandemic is only speeding that process along. Qantas, KLM Royal Dutch Airlines, Virgin Atlantic Airways, and Corsair have all retired their Boeing 747s months ahead of schedule while Air France abruptly retired its Airbus A380 fleet in May, 11 years after its first flight for the flag carrier.

It wasn't for lack of comfort, as most travelers loved the additional space offered by both aircraft, which allowed for amenities not found on most single-engine jets. The early days of the 747 saw the iconic hump used for cocktail lounges or a restaurant in the skies while the A380 is known for being the only commercial airliner to have an in-flight shower, which Emirates offers to first class passengers.

Rather, the massive aircraft became a casualty of their manufacturers' ambition in crafting newer planes to do the job cheaper and more efficiently than the behemoths they once touted.

Too many engines

Bigger used to be better in aviation, with the Boeing 747 affectionately nicknamed "Queen of the Skies" since it could fly longer with more passengers than its competitors. But taking the place of the A380 and 747 are not larger jets but smaller ones.

Efficient, twin-engines planes are now all the rage among airlines with the likes of the Boeing 787 Dreamliner and Airbus A350 XWB replacing their predecessors as the flagships of the fleet despite their smaller stature. Having four engines no longer means what it used to and airlines are realizing they can get by with fewer.

The Boeing 747 once opened routes that were previously inoperable nonstop but now, the 787 and A350 take up a majority of the spots on the list of world's longest flights with the latter boasting a top range greater than the newest 747, according to Airbus. An A350-900 currently flies the world's longest route between Singapore and Newark, on temporary hiatus due to the pandemic.

Airlines also no longer need three and four-engine planes to cross the Atlantic with planes as tiny as the Airbus A318 making the overwater journey between New York and London on a near-daily basis before the pandemic. Revised government regulations in the 1980s to allow twin-engines planes to fly overwater routes spurred the development of jets like the Boeing 777 and Airbus A330 to fly those routes and make them more lucrative.

Efficiency is now the name of the game. Qantas CEO Alan Joyce, whose airline has operated the Boeing 747, Airbus A380, and Boeing 787 Dreamliner, once said that his airline could fly two Dreamliners for less the price of one Airbus A380 flight with the A350 likely boasting similar economic advantages.

Not only are the jets more efficient to operate, but they're also cheaper to purchase. The Airbus A380 costs a whopping $445.6 million, according to Airbus' most-recent price list, while the Boeing 747-8i goes for $418.4 million, according to Boeing.

The largest Airbus A350 XWB and Boeing 787 Dreamliners, on the other hand, are cheaper to buy at $366.5 million and $338.4 million, respectively.

Though airlines often get discounts based on a variety of factors including the relationship with the manufacturer and order size, the larger jets still end up costing more than the smaller twin-engines.

Customers want flexibility

Flying two Dreamliners in lieu of an Airbus A380 would only mean a loss of capacity of 12 seats for Qantas, according to SeatGuru, assuming the A380 flight completely sells out but offers the flexibility to fly an additional frequency. Instead of one flight between Los Angeles and Sydney, it can theoretically fly two and attract customers who need a flexible schedule.

Airbus had designed the A380 to carry as many people as possible so that airlines would be able to fly fewer flights. Instead of flying multiple flights between two cities, airlines could save money by flying just one A380 flight and cramming as many passengers into one plane.

What that would've meant, however, was fewer flights and less flexibility for travelers who don't want to rely on just one flight per day. Very few airlines used the model as intended and the A380 came too late as Boeing was already knee-deep in the 787's development by the time the A380 took its first flight.

Instead of fewer flights on larger aircraft, the wave of next-generation aircraft opened up more nonstop routes for airlines as low-demand routes were made profitable thanks to the efficiency of the aircraft. Two airlines, British Airways and Norwegian Long Haul, pioneered the model, with the duo opening of a series of routes to secondary markets that wouldn't normally see non-stop routes to major hubs.

British Airways uses its Dreamliners to fly from London to small US cities like Charleston, South Carolina; Nashville, Tennessee; and Pittsburgh, Pennsylvania while Norwegian flies from cities across Europe to markets like Denver, Colorado; Austin, Texas; and Seattle, Washington.

Opulence lost

The incredible excess of space on both jets opened up a world of possibilities for airlines that started in the early days of the 747 when entire sections were turned into social areas and lounges. Some airlines continue that trend today as Qatar Airways, Korean Air, Emirates, and Etihad Airways all offering bars and lounges for premium passengers onboard their Airbus A380s.

Each airline has its own unique offering with Korean Air setting up a retail shop onboard its A380s while All Nippon Airways has sky couches for families in economy. Emirates' A380s are perhaps most well known for the onboard showers offered exclusively to first class passengers traveling on the double-decker jet.

The CEO of Emirates – the world's largest A380 operator – lamented the end of the A380 program in an interview with Business Insider's David Slotnick, saying "nothing is going to be as good" as the superjumbo for passenger experience.

Extra space on jets like the Dreamliner and A350 is a luxury that most can't afford to waste, though some have gotten creative. Virgin Atlantic Airways, namely, did away with its signature onboard bars for the new A350-1000 XWB flagship but crafted a social area for business class passengers.

Losing the dual-level aircraft also coincides with the loss of the ultra-premium first class cabins that have been steadily disappearing as airlines downsize their fleets. Air France, Qantas, and United have all opted not to install first class cabins on their A350 and Dreamliner fleets despite having them on their quad-engine jets, opting instead for larger business class cabins or more modern business class suites.

Even for economy passengers, both jets offered more space to stretch out with a larger cabin feel. The Airbus A380, its manufacturer touts, was highly rated for passenger comfort and created a website, IFlyA380.com, so travelers can find A380-specific itineraries.

Flying precious cargo

Boeing attempted to reinvent the 747 product line with the 747-8i, a longer version of the jet with new General Electric engines to offer greater efficiency. Despite its impressive upgrades, the newest variant failed to spur customer interest. With only a handful of passengers airlines buying them, the writing was on the wall for the 747.

All Nippon Airways was the last new airline to take delivery of the Airbus A380 in March 2019 and while the manufacturer had likely hoped the iconic jet would be saved by another new order, the coronavirus pandemic ensured that wouldn't happen. Emirates will be the last customer to take delivery of the jet that may roam the skies for another two decades before the last of its kind is retired.

Unlike its Boeing counterpart, the A380 has not been able to make the transition into the cargo realm, except for one airline that hollowed out its sole A380 to increase cargo capacity during the COVID-19 airlift. There are few uses for secondhand A380s, with demand undoubtedly dropping even more with the pandemic.

As for the Boeing 747, its legacy will continue by the cargo carriers who can make use of every inch of space the jet has to offer. Either UPS Airlines or the Volga-Dnepr Group, both cargo carriers, will likely take delivery of the final 747-8 within the next two years while passengers airlines turn their attention to the new twin-engine Boeing 777X.

The Airbus A380 may have bested the 747 in size but not in legacy. The Boeing jet has survived for over a half-century and has one more high-profile placement to go, flying the president of the United States as Air Force One when the aging incumbents are replaced by new 747-8i jets.