Flexibility is no buzzword in defense and commercial aviation—it can be the difference between success and disaster. In the unlikely event of an engine loss away from home base, every hour will matter, and operational availability, expense, and strategic options all hinge on it. The Boeing 747, “Queen of the Skies,” revolutionized quietly: the ability to carry a fifth engine on its wing.
One thing that no other commercial aircraft has, however, is that the 747 features reinforced attachment points on the lower surface of its wings. They allow engineers to add a spare engine and a custom-fabricated support strut, essentially converting the engine into cargo. The fifth engine does not drive during flight—it’s huge, six tonnes’ weight, sandwiched between the fuselage and innermost engine on the left wing.
Although the principle is not that hard, the implication is enormous. The strut has a winching mechanism in it that holds the engine in place flawlessly and keeps it tight for as long as the flight lasts.
It is not easy to fly with one more engine. Pilots must compensate for the added weight and drag, making minute power and control trim adjustments to remain stable. The extra weight also affects range, at times needing extra refueling stops, like on a Qantas Sydney-to-Johannesburg flight that needed a Perth refueling stop.
But this skill is not just an antique engineering oddity—it’s a practical tactical advantage. In January 2016, a Qantas 747 was diverted at Johannesburg following a failure of a Rolls-Royce engine. It would have taken weeks to ship a spare by ship, and chartering a freighter plane was expensive and time-consuming. Solution: Ship the spare engine on a scheduled flight on the fifth-engine mount of the 747.
Locally, the replacement of engines was done, and the two aircraft were placed in service straight away, saving valuable time and finances. As Qantas explained, “having a 747 overseas and not flying any routes is an expensive venture.”
Five-engine 747 history in Johannesburg goes back decades. In 1971, South African Airways accepted its first 747 (registration ZS-SAN), which came from the factory with a fifth engine already installed. Local spares were unavailable, and no freight aircraft to transport the whole 747 engine, so they decided to take it out on the plane itself. That plane, Lebombo, sits today in the South African Airways Museum still retaining its fifth engine—a flying ingenuity tip of the hat that to this day still continues.
From a military perspective, the ability to airlift heavy, intricate spare parts quickly can be the key to successful missions and costly delays. Aircraft like the 747, with this fifth-engine technology, have a clear logistical advantage.
They avoid the deceleration of regular shipping, do away with the reliance on specialty cargo carriers, and allow fleets to remain airborne even in the remotest areas.
The record of five-engine 747 operations is more than a technical footnote; it’s a testament to how groundbreaking engineering evolves to meet practical needs in civilian and military aviation alike.
Even though Qantas retired its 747 fleet in 2020, closing an iconic chapter in aviation history, the legacy of these missions still shapes the design and operation of the next generation of airlifter aircraft. That level of flexibility is a benchmark in modern aviation.