Boeing has finalized a $56 billion agreement to build 150 777X aircraft for Dubai's Emirates Airline.
The order's value is based on list prices, which can vary greatly after negotiations.
The 777X is a larger and more fuel-efficient model of Boeing Co.'s popular 777 wide-body and Emirates is the world's largest operator of those planes.
The companies first announced a commitment to do the deal at the Dubai Airshow in November. Included in the order are 115 777-9Xs and 35 777-8Xs. The list price for the 400-passenger 777-9X is $377.2 million, while the list price for the 777-8X -- which can carry up to 350 passengers -- is $349.8 million.
Emirates Airline also has purchase rights for an additional 50 aircraft. If exercised, it could raise the value of the deal to about $75 billion, again, at list prices.
Production of the 777X is expected to start in 2017, with first delivery targeted for 2020.
Last month Boeing, based in Chicago, signed a deal for five Japanese companies to make key components for its twin aisle 777X jets but the contract doesn't include the wings, which were a source of delays for the 787 Dreamliner. The Japanese manufacturers will make about 21 percent of the new plane's structural components, including fuselage sections and landing gear wells.