The U.S. plane maker expects to start production in 2017 and hopes to deliver the first aircraft by 2020. The deal involves 115 400-seat 777-9Xs and 35 smaller 777-8Xs, with Emirates having the option of extending the order by 50 aircraft, taking the total value of the deal to $75 billion.
Emirates currently operates 138 777s and has 208 aircraft in the pipeline, including the newer model of the 777 aircraft. Emirates order takes Boeing's order book for the 777X to around 300 planes for six different customers.
The deal was initially announced last November at the Dubai Air Show and the finalized deal comes days before the Farnborough International Air Show in the U.K.
Emirates canceled a deal with Boeing competitor Airbus for 70 A350 wide-body planes valued at $16 billion. Airbus said the purchase was canceled after "discussions with the airline in light of their fleet requirement review."