Dubai-based Emirates Airline has finalized its order for 150 Boeing 777Xs, previously announced at last November’s Dubai Airshow. The deal comprises 115 777-9Xs, 35 longer-range 777-8Xs and includes purchase rights for a further 50. The order, valued at $56 billion at current list prices, was part of the largest product launch in commercial jetliner history. If all options are confirmed, the value of the deal could increase to around $75 billion at current list prices.

Emirates is already the world’s largest 777 operator.

“With the order for 150 777Xs, Emirates now has 208 Boeing 777s pending delivery,” Emirates president Tim Clark said. “Today Emirates operates more than one in every 10 Boeing 777s aircraft built.”

Clark said the 777X will offer “operational flexibility in terms of range, more passenger capacity and fuel efficiency, and we look forward to inducting them into our fleet from 2020.”

The 777X will be powered by GE Aviation’s GE9X and an all-new high-efficiency composite wing with a longer span than today’s 777.

Design of the 777X is underway, with production due to begin in 2017 and initial deliveries targeted for 2020. To date, the 777X has accumulated 300 orders and commitments from six customers.

Boeing said the 777-9X model will be 12% more fuel efficient than any competitor and the 777-8X will have a 5% advantage over competitors.