Qatar Airways has placed an order for 10 777-8Xs and four 777 Freighters.
"Acquiring technologically advanced airplanes such as the 777X is integral to our expansion strategy," says the airline's chief Akbar Al Baker. "With the addition of these 777-8Xs to the 50 777-9Xs already on order, we are confident of continuing the tremendous legacy of the 777."
He adds that Qatar's 777F order "underpins the value that this airplane has also brought to our rapidly growing cargo operations". The Doha-based Oneworld carrier already has eight 777Fs in service, Flightglobal's Ascend Fleets database shows.
Boeing says design of the 777X is under way and production is set to begin in 2017, with first delivery targeted for 2020.
With the Qatar order, the 777X has accumulated 320 orders and commitments from six customers worldwide.
The other customers comprise All Nippon Airways, Cathay Pacific Airways, Emirates Airline, Etihad Airways and Lufthansa, Ascend Fleets shows.