The 777X will be an updated version of Boeing's best-selling 777, Boeing's second-biggest plane, used by airlines for very long international flights. For the new version, Boeing plans to replace aluminum wings with wings made from a lightweight, high-tech plastic and make other improvements that will make the plane more fuel-efficient.
Before the Cathay announcement Friday, Boeing had booked orders and commitments for 259 of the planes worth $95 billion at list prices. The Cathay order boosts the list to 280 planes worth more than $102 billion.
Cathay is already a big 777 customer, with 55 in its fleet.
Boeing builds the current 777 in Everett but it is deciding where it will build the 777X.