Boeing will expand seating on its new 777-9X by 20 seats.

An authoritative aviation industry web site says Boeing, at the suggestion of a Mideast airline customer, will add 20 more seats to its planned 777-9X aircraft.

Aspire Aviation reports that Boeing will lengthen the fuselage of the updated plane by some 8 inches and reconfigure the interior to accommodate those additional seats. The extra seats will give the big twin jet a capacity in excess of 400 seats.

Boeing is updating its popular 777 with new, longer composite wings and new engines and a stretched fuselage to improve its capacity and efficiency.

The 777X models will be built at the company’s Everett final assembly plant. Boeing is building a new wing fabrication plant at Everett to create the new folding-tip wings.