Emirates Airline sealed a deal worth $56 billion for 150 of Boeing’s new 777X planes, helping make the 777X debut the largest product launch in commercial jetliner history, the companies announced today.

The deal was first announced at the 2013 Dubai Airshow in November and includes a combination of 115 777-9Xs and 35 777-8Xs. Emirates, which is the world’s largest operator of Boeing’s 777 jets, also has the purchase rights for an additional 50 planes. If exercised, the deal value would increase to about $75 billion at list prices.

“With the order for 150 777Xs, Emirates now has 208 Boeing 777s pending delivery, creating and securing jobs across the supply chain,” Sir Tim Clark, Emirates president, said in a statement. “The 777X will offer us operational flexibility in terms of range, more passenger capacity and fuel efficiency.”

Boeing BA has received 300 orders and commitments from six customers worldwide for its 777X line, which is expected to begin production 2017 and deliver in 2020.

The 777X planes are more fuel efficient than comparable models currently in service. The 777-9X will be 12% more fuel efficient and the 777-8X 5% more fuel efficient than competitors at all ranges.

The new models also include a more advanced commercial engine, the GE9X by General Electric Aviation, and a high-efficiency composite wine that has a longer span than current 777 jets.