EVERETT (United States) – In a mammoth factory that a Boeing manager calls the largest “on the planet” by volume, the aviation company is assembling the world’s biggest double-engine aircraft: the 777X.

The Seattle-area plant is filled with several of the flying behemoths at various stages of production, with the snow-capped mountains of Washington state peeking out from behind an open hangar door.

Boeing’s Everett plant will be tasked with assembling three versions of the jet: the 777-200 cargo plane, which is based on a 777 model already in service; the next-generation 777-9 which is still being certified; and the 777-8, another new model that is slightly smaller than the 777-9.

The company has been under heavy scrutiny following a near-catastrophic January incident on a 737 MAX aircraft operated by Alaska Airlines, which saw a door plug blown out mid-flight.

Several other high-profile mishaps involving its aircraft – although none on 777s – have upped the pressure on the manufacturer, with the company announcing steps to enhance safety and quality control in response.

Company officials insist Boeing’s long-term prospects remain bright, however, due in part to the new 777X.

The 777 – a stalwart of long-haul commercial aviation – is “the most successful twin aisle airplane of all times,” Brad Till, a managing director at Boeing, told journalists during a factory tour held late last month.

Boeing has received more than 2 250 orders for 777 models since the plane family was launched 30 years ago, and 777s have flown roughly 3.9 billion passengers on 15.9 million flights.

Boeing unveiled the most recent incarnation of the jet, the 777X in 2013.

Deliveries were originally targeted for 2020, but the company hit obstacles during the certification process, with orders now expected to be fulfilled starting in 2025.