An unusual sight: Qantas used this 747 to transport a new engine to a stranded aircraft. Courtesy of Qantas Passengers on a recent Qantas Airways flight from Sydney to Johannesburg might've noticed some very unusual cargo on board.

The airline patched a fifth engine onto the wing of the Boeing 747-400 jumbo jet. The engine was destined for another aircraft that became stranded after experiencing mechanical trouble.

The massive 747 was actually designed to transport an extra engine. In fact, this method was adopted decades ago, though it is rarely used. Qantas last transported a fifth engine in 2011.

Other transportation for the nearly 14,000 pound Rolls-Royce turbofan engine, like ship transport or charter air cargo, could have taken weeks or even months, the airline said in an official press release.

After transplanting the new engine, workers in South Africa were able to return the stranded aircraft to service in less than 24 hours.

The extra passenger did not go unnoticed, however; other, ticket-holding riders posted pictures on social media and the airline's official instagram featured the strange sight:

An extra engine on a jumbo? Find out more in our bio. #Qantas #avgeek #B747 #✈️ A photo posted by Qantas (@qantas) on Jan 5, 2016 at 8:46pm PST Jan 5, 2016 at 8:46pm PST

The engine was not producing power, however, and the drag produced by the massive, hitchhiking turbofan required the flight to make a quick refueling stop in Perth, Australia.