The airline just made a historic order for hundreds of new aircraft.

United Airlines is making historic upgrades to its fleet of planes. On Tuesday, the Chicago-based airline announced that it would order up to 200 new Boeing 787 Dreamliner planes—the largest-ever order of widebody jets for a U.S. carrier.

The new planes are a significant part of United’s ongoing plan to enhance its in-flight experience for passengers, which includes previous orders for smaller new planes, like the Boeing 737 Max, adding new Polaris business-class seats to more jets, and refurbishing the interiors of existing aircraft with perks like in-flight entertainment screens at every seat, Bluetooth connectivity, and la

As part of the new Boeing deal, United confirmed it would purchase 100 new Dreamliners, with options to purchase up to 100 more of the widebody jets, which are a favorite among frequent travelers on long-haul flights for their spacious interiors, larger windows, LED mood lighting, and higher humidity settings to help reduce jet lag. The airline said about 100 of the new Dreamliners would be earmarked to replace older planes, like the Boeing 767 and 777 jets.

“Our widebody fleet will be re-energized by these new 787 deliveries and further strengthen what we do best: connect people and unite the world with modern, customer friendly and fuel-efficient aircraft,” Andrew Nocella, United Airlines’ executive vice president and chief commercial officer, said in a statement on Tuesday. “United is uniquely positioned to capture international travel demand thanks to our global network, fleet size and gateway hubs. This combination represents a significant advantage for our business for years to come and another reason for business and leisure customers to choose United.”

All of United’s Dreamliners are outfitted with four cabin classes: Polaris business class, Premium Plus, Economy Plus, and regular economy. Among the best premium seats on a U.S. airline, every Polaris seat lies flat, has a memory foam layer, and comes with a gel pillow, mattress pad, and duvet from Saks Fifth Avenue. There’s also 16-inch seat back screens, as well as pajamas and slippers available on request for an extra dose of coziness.

The Premium Plus cabin, United’s version of premium economy, has seats with a six-inch recline, 13-in seatback screens, an amenity kit, pillow, and blanket.

Beyond passenger comfort, the new planes will also slash carbon emissions on each flight. The 787 Dreamliners are up to 25 percent more fuel efficient than the older planes they’re replacing, thanks to new engines, lightweight composite materials, and more efficient design. The airline has an ambitious goal to reduce its greenhouse gas emissions by 100 percent by 2050 without relying on carbon offsets. The new Dreamliners will range in sizes between the -8, -9, and -10 models in order to serve a wide variety of routes and will start to be delivered to the airline in 2024.

The momentous aircraft deal—worth an estimated $16 billion, according to Jonathan Root, senior vice president for Moody’s Investors Service—comes as United has made major expansions to its long-haul route network over the last year, launching 10 new nonstop transatlantic routes to destinations like Amman, Jordan; Ponta Delgada in the Azores; Bergen, Norway; and Palma Mallorca, Spain.