Emirates, the largest operator of the Airbus A380, said on Wednesday it is ordering two more of the double-decker superjumbos to be delivered in the fourth quarter of 2017.

The two new A380s, to be fitted with Rolls-Royce Trent 900 engines, will increase Emirates’ A380 order book to 142, according to a statement from the Dubai-based airline.

Emirates has 75 A380s in its fleet and a further 67 on back order, including the two new orders announced on Wednesday. The order is valued at $865.2 million, according to Airbus’ price list, though it is common for airlines to receive discounts on orders.

While Emirates did not elaborate on the reason for ordering two new A380s, an individual with knowledge of the order, told Gulf News that the Dubai airline is taking the two additional aircraft from an order that was originally scheduled for Japanese budget carrier Skymark.

Skymark had its order for six A380s cancelled by Airbus in 2015 after the airline declared bankruptcy in the same year. Two of the Japanese carrier’s partially built A380s have since sat at Airbus’ facilities in France as the planemaker sought a buyer.

Emirates’ newly ordered superjumbos will be fitted with two classes, according to the statement, increasing the airline’s business and economy-only A380 fleet to 17. Emirates has been flying the two-class A380s since December 2015.

Emirates President Tim Clark said in a statement that the superjumbos have been a “big success” for the airline. “It’s a boon for our operations to slot constrained airports and we get a lot of positive feedback from our customers,” he stated.

The order comes as Emirates pushes Airbus to commit to building a newer, more fuel efficient version of the A380. Airbus has downplayed the prospects of an A380neo (new engine option) and last year one of its executives suggested it could soon stop making the superjumbo altogether. Airbus has since backed away from those comments.