Flexibility, whether in the military or civilian aviation, is more than a slogan—it’s sometimes a matter of life and death. When a plane suffers a mechanical failure in the field, time will soon be the enemy. Each hour a plane sits out affects operations, expenses, and strategic planning.
The Boeing 747, popularly referred to as the “Queen of the Skies,” brought forth a brilliant innovation that deceptively transformed how militaries and airlines cope with their fleets: the possibility of having a fifth engine on the wing.
Unlike all other airliners, the 747 has reinforced attachment points on the wings. There, a spare engine can be strapped to a support strut, basically using a necessary part as luggage. This fifth engine is not used in flight—it’s a dead weight, about six tonnes, placed between the fuselage and the innermost engine on the left wing.
Even though the concept might sound easy, the impact is not that easy. The strut incorporates a winch mechanism that holds the engine in place firmly while on the road and ensures that it does not shift even under tough conditions.
It is a sensitive operation to carry this additional weight. Flight handling and power settings have to be controlled very carefully by pilots to counteract the unbalanced loading and increased drag. The increased weight decreases the range, sometimes necessitating unplanned refueling. An exemplary well-documented case was when a Qantas aircraft flew between Sydney and Johannesburg with an extra fifth engine, which required refueling at Perth.
Beyond its engineering genius, the fifth-engine configuration provides a concrete strategic benefit. In Jan 2016, Qantas had one of its 747s stuck in Johannesburg with a failed Rolls-Royce engine. Having one flown in by ship would take weeks, and leasing a freighter was expensive and slow.
What to do? Take the 747 itself in on a passenger flight with the spare engine. When it did come, however, the new engine was installed and the two planes were in service again in no time, conserving time and money. It is a costly headache, says Qantas, to have a 747 out of action overseas. The idea has been around for years.
In 1971, South African Airways took delivery of its first 747 with a fifth engine already fitted at the factory. There were no locally available spare engines and no cargo planes to transport a whole 747 engine. The only recourse was to take it up in the air attached to the plane itself.
That pioneering aircraft, Lebombo, now hangs in the South African Airways Museum, still sporting its fifth engine—a testament to creative flight thinking that remains.
Logistically and militarily, having the capability to ship critical, oversized components on time is the difference between a successful mission and expensive delays. Planes such as the 747, which have fifth-engine capacity, avoid normal shipping delays, minimize dependence on specialty cargo aircraft, and maintain operations despite flying in distant or hard-to-get areas.
The history of the five-engine 747 missions is more than a fascinating engineering anomaly. It is a testament to where practical innovation and genuine necessity converge in the skies. As Qantas retired its 747 fleet in 2020, closing an iconic chapter, what was learned on those flights still influences the design and functionality of modern airlift aircraft. The strategic advantage of such versatility is a pattern for the modern age of flight.