Qantas has released images and a video of one of its B747 jumbos "ferrying" an extra engine to Johannesburg this week.
As flagged up on our forum, the six-tonne Rolls Royce engine was attached to flight QF63 from Sydney to Johannesburg, where it was needed for another B747 aircraft.
Qantas said that Boeing's jumbos are fitted with the capability to carry a fifth (unpowered) engine, fitted between the body of the aircraft and the inner-most engine on the port side.
It's rare for engines to be transported in this way (the last time Qantas did so was in 2011), and the extra weight and drag from the engine meant the flight had to refuel in Perth.
But Qantas said it undertook the task "to get our customers and our aircraft on their way as quickly as possible".
The spare engine removed from Qantas' B747 in Johannesburg will then be sent back to Sydney the more conventional way - by boat.