DULLES, Va. – United Airlines presented its first Boeing 787-10 Dreamliner at Washington Dulles International Airport.

The event marked the first time United revealed the interior of the plane, which it received two weeks ago.

United already had two smaller versions of Dreamliner in its fleet, 787-8 and 787-9. But "Dash 10" is the largest version of Boeing's Dreamliner line. Boeing delivered the first 787-10 only in March last year, when Singapore Airlines became the first carrier in the world to receive one.

Now United became the first North American airline to receive 787-10. The carrier is also the only airline in the world that has all three Dreamliner variants in its fleet.

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The United 787-10s – which are 18 feet longer than the 787-9 – will have 318 passengers. This includes 44 new Business Class "Polaris" classrooms and 21 Premium Plus classrooms, United's newest class of services, which debuted earlier this year. It is not yet extended to the United fleet but is installed on all 14 787-10 that United has ordered.

Complementing United's 787-10 layout is 54 seats in addition to the Economy Plus legs and 199 in the standard coach.

By comparison, United's 787-8 seat has 219 passengers and its 787-925 seat.

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After delivering from Boeing, United flew 787-10 to Washington Dulles for some additional changes before entering the passenger service.

"Dreamliner's first stop, once we were delivered, was our Dulles / DC center, where we started making post-delivery changes, making the plane more specific to United," Maddie's spokeswoman says King in the Today of the Sky blog. "All of our Dreamliners are going to Dulles first, where we install things like brand names and our flying entertainment system.

Polaris business class cabin is United's latest update to premium product. It was launched in the fanfare in the summer of 2016 and was generally well received by customers, although some have mumbled about how slow the product was released in United's international fleet.

The 21 premium premium class Premium Plus class is a new offer that allows United to match similar products offered by international airlines such as Singapore Airlines, Lufthansa, Air France, British Airways and more. More recently, US airlines have joined this trend. American and Delta have already released their versions and are further on launching this product.

In the economy booth, United seats have 34 inches of "pitch" – a standard measure of space space – in Economia Plus and only 31 centimeters in the standard economy.

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