Qantas once flew a 747 with 5 engines to South Africa

One of Qantas’ Boeing 747s was stranded in South Africa after one of its engines was damaged, leaving Qantas in a tough spot. In order to get a new engine from Australia to South Africa, the airline has a number of options which were to use a specialised air freight carrier as the engine was too large. This would have been fairly quick but quite expensive. The second option was to ship via sea, which was obviously cheaper but would take too long. The third option was attaching the spare engine to a scheduled flight going to South Africa.

Ultimately, the airline chose to attach the spare engine to a Boeing 747-400. Unknown to many is that there are anchor points under the wing of the B747s, and these can be used to secure various objects. A spare engine may be one of them. In order to fly safely with the extra engine, the pilots had had to; An additional engine obviously made the plane heavier, resulting in a fueling stopover in Perth

• adjust for the unbalanced weight distribution of the aircraft as it was heavier on the wing with 3 engines.
• Increase power to compensate for increased drag on the heavier wing.
• Add a fuel stop (The normal route was a direct flight from Sydney to Johannesburg, but on this flight, a stopover in Perth was necessary).
• Reduced speed (flew at Mach 0.78 instead of 0.85) to minimise vibrations and stress on airframe.

The flight was successful, and the spare engine was installed on the grounded aircraft without further incident, allowing both jets to fly back to Australia.