Qatar Airways has placed an order for 100 Boeing 777-9X aircraft in a deal worth £24 billion at list prices.
At this week's Farnborough Air Show, the Gulf airline finalised an order for 50 B777-9Xs and increased its order with an additional 50 B777-9X purchase rights.
The aircraft is due for delivery from 2020.
Qatar Airways CEO Akbar Al Baker said: "It has been a year of many new beginnings for Qatar Airways, with the opening of our new home at Hamad International Airport and now these further aircraft orders for our fleet.
"The Boeing 777 has been a backbone of our operation and our relationship with Boeing will continue to grow and develop as we go on investing in the equipment that we value and trust. This will enable us to continue to deliver a signature five-star service to our passengers."
Boeing claims its 777-9X will be 12 per cent more fuel efficient than any competing airplane. Its design is underway and production is set to begin in 2017, with first delivery targeted for 2020.
The airline said in a statment: "To date, the 777X has accumulated 300 orders and commitments from six Boeing customers worldwide."