The question about why some airlines operate quad-engined commercial airliners is mostly a legacy question. No commercial quad-engined passenger aircraft are produced today, and there are no concrete plans to bring them back, apart from the supersonic Boom Overture. Barring Russia producing more obsolete quad-engined Il-96 passenger jets, the last passenger quad-jets were delivered in 2021 as Emirates received the last Airbus A380.

Boeing 747-8s remained in production until 2023, but they were freighters. Put another way, classic tube-and-wing quadjets will completely disappear from the skies as a scheduled passenger airliner; it's just a matter of time. Passenger quadjets will be exceedingly rare after the 2030s, but may persist into the 2040s in very low numbers.

The World's Remaining Passenger Quadjets

As of 2026, no trijets are remaining in regular scheduled passenger service, and some types of the world's quadjets, like the Boeing 707, are retired as regularly scheduled passenger aircraft. The remaining quadjets are the Airbus A340, Airbus A380, Boeing 747, and Il-96. Starting with the easiest first, there is only a single Il-96 currently in active service, and that aircraft is in service with Cuba's flag carrier, Cubana de Aviación.

Cubana has two examples in service, of which only one is active, although it's unclear if there is enough fuel on the island to operate it as of the time of writing. Some Russian airlines also operate Il-96s, but they are mostly for governmental or cargo use. This article will focus on only quadjets used for scheduled commercial passenger flights.

Cargo aircraft and charter aircraft (like Atlas Air's charter passenger 747-400s) are not regularly scheduled commercial passenger airliners and so are outside the scope of this article. Leading reasons why airlines generally don't want to operate quadjets are that they are less fuel-efficient, are more difficult to maintain, and are less reliable. The decreased reliability is because it's more likely that something is wrong with one of four engines than with one of two. That said, quad-jets exist and are available and are generally not capital-intensive due to their age.

Ultra Large Widebody Aircraft

One of the reasons why there are quad-engined aircraft is that four engines are needed to power ultra-large widebody aircraft. Boeing developed the Boeing 747 in the 1960s, and at the time, it was one of the first aircraft to use jet engines. Those engines have been improved over time, but the size of the aircraft requires four engines. In the early 2000s, Airbus assessed that the future of aviation was the hub-and-spoke model, and it assessed a demand for an ultra-large widebody aircraft.

In response, it built the A380-800 double-decked aircraft with the intention to stretch it to the even larger A380-900 later on. That never happened, and Airbus was wrong. The future of long-haul commercial aviation was mid-sized, widebody, long-ranged, fuel-efficient aircraft like the Boeing 787 Dreamliner and the Airbus A350. One of the problems for Airbus is that it was blindsided by the engine manufacturers, who assured Airbus that there were no more efficient engines on the horizon. Before Airbus had even launched the A380, but after it had committed to it, Rolls-Royce and GE unveiled the more efficient Trent 1000 and GEnx for the Boeing 787 Dreamliner.

Airbus only managed to sell 251 Airbus A380s, with half going to Emirates. This was not enough for Airbus to recoup the development costs, although it did help in ending Boeing's rival Boeing 747-8 program. Boeing's Dreamliner also helped undermine the 747-8. While Boeing sold 155 Boeing 747-8s, about enough to break even, it only sold 48 passenger variants, with the remainder being freighters and business/VIP jets. By the 2010s, it was clear the age of quadjets and ultra-large widebody aircraft was over.

The Need For ETOPS

One of the primary drivers for quadjets was the requirement that twin-engined aircraft could not fly beyond 60 minutes from an emergency diversion airfield. This was a safety precaution in the event of engine failure and encouraged airlines to purchase trijets and quadjets even when they were less fuel efficient, and two engines were now powerful enough to fly them. But then Boeing took the major decision to develop the twin-engined Boeing 767, which received a 120-minute ETOPS certification, allowing it to fly up to two hours from the nearest diversion airport.

Airbus soon followed by developing the twin-engined A300. Airbus built on its A300 success by developing it into the quad-engined A340 and the twin-engined A330. These are sister aircraft and were a hedge by Airbus so that airlines could purchase a quad-engined alternative to fly long-haul routes away from diversion airports. But as ETOPS exemptions grew, the A340 was increasingly seen as unneeded.

Airbus delivered around 1,500 classic twin-engined A330s and only 380 quad-engined A340s. It ended A340 production in 2012 but upgraded the A330 to the A330neo in 2018. The A330neo comes with a new wing and next-generation engines. Modern twin jets, like the A330neo, A350, and Boeing 787, have ETOPS certifications that practically allow them to fly almost any viable commercial route. The A350 has the highest ETOPS certification, and it can essentially fly anywhere other than over Antarctica.

A Legacy & A Lag

Commercial aircraft are extremely expensive and take time to replace. Once a commercial jet has been purchased, it can expect to fly for around 20–30 years in commercial passenger service. As quadjets are inefficient, the pressure to retire them earlier is greater. It may then fly another ten or so years as a converted freighter, although A380s are ill-suited as freighters. This means that quadjets can be expected to persist in commercial service for two to three decades after production has ceased.

Lufthansa is now one of the last major commercial airlines operating its A340s as scheduled passenger airliners. It plans to retire the last of the 14 examples it has remaining in service by October 2026, or 14 years after the last were produced. Another operator is Edelweiss Air, which has three A340s remaining, and these are to be replaced by A350s by around 2027. More A340s remain in service as cargo aircraft, as government aircraft, and for sanctioned airlines. More on that below.

The Boeing 747-400 remains in scheduled passenger service with Air China (three examples) and Lufthansa (eight examples). These are expected to retire after the 2027 summer season, or 22 years after the last passenger version was delivered. The A380 is designed to operate for around 20 to 25 years, with Emirates trying to get as much service out of them as possible and not retire them until around 2040. Still, other airlines have seen A380s as white elephants, with Air France, Malaysia Air, and others retiring them in 2022. Other airlines are itching to rid themselves of the jet as soon as their delayed replacement aircraft arrive.

The Sanctions Distortions

Most of the world's major airlines operate based on open market forces. They will replace their aging aircraft when they become too expensive to maintain and too fuel-inefficient relative to the new aircraft available on the market. However, sanctions create a major distortion in the market. Countries like Russia, Venezuela, Iran, North Korea, and Cuba are under US and/or Western sanctions, meaning it is impossible for them to acquire new Boeing and Airbus aircraft.

In these conditions, the calculus goes from operating the most economically feasible aircraft to operating any aircraft available. Efficiency is a luxury these countries do not have. Their options are to build their own aircraft, keep their old aircraft in service for longer, purchase retired aircraft on the black market through shelf companies, or some combination of those options. Russia is currently working to replace imported Western components and restart production of its own aircraft. But this forces them to resurrect obsolete designs, possibly including the quad-engined Il-96.

Russia had retired its Boeing 747-400s, but between three and four of these have been hauled out of retirement, pushed back into service for domestic routes in an effort to have enough seat capacity. Iran has been purchasing retired A340 quadjets on the black market. These have the advantage of being available, having flight hours remaining, and being relatively easy to maintain because they are older. There are also plenty of second-hand spare parts floating around from cannibalized aircraft.

Delivery Distortions & Financing

While sanctions may be the biggest distortion keeping old jets flying in select countries long after being phased out elsewhere, another is delivery delays. This has impacted airlines like Korean Air, Qatar Airways, and Lufthansa. They have wanted to retire many of their older aircraft (e.g., A380s, 747s, A340s, and older 777s) for a while, but they can't because their Airbus and Boeing A350, 787, and 777X orders are delayed. This has forced them to hold onto these quadjets for longer, and it has contributed to the Boeing 747-400 and 747-8 remaining in passenger service for longer.

Financing is another major limiting factor. This typically affects smaller airlines in poorer countries, as well as in sanctioned countries. If an airline is unable to get the loan it needs to purchase an aircraft or secure a long-term lease, then it is effectively locked out of the market for purchasing new aircraft. These airlines may be forced to operate ancient aircraft, including quadjets, that are expensive to operate, but cheap to buy.

There are other market distortions that may keep quadjets in service for longer. One example is London-Heathrow, where slots are limited and so airlines are incentivized to continue operating high-capacity airliners, like the A380, to make as much use of available slots as possible. Finally, while not a market distortion, Emirates is a rare example of a classic high-capacity hub-and-spoke model airline that the A380 is well-suited for.