The Australian carrier Qantas has canceled an outstanding 2006 order for eight Airbus A380 airplanes, adding to the uncertainty about the fate of the world’s largest passenger aircraft.

Qantas said in a statement on Thursday that it would instead upgrade the 12 A380 planes that it already had, adding that “these aircraft have not been part of the airline’s fleet and network plans for some time.”

Airbus has already said the giant plane’s days could be numbered, acknowledging a year ago that it would have to end production if Emirates, its only major customer, did not order more.

A bet that airport congestion and increased international travel would lead to demand for larger planes, the A380 was pitched as a way for airlines to transport more passengers with limited landing slots. The aircraft can carry more than 500 passengers.