Korean Air Chairman Cho Won-tae, right, shakes hands with Stephanie Pope, president and CEO of Boeing Commercial Airplanes, after signing a memorandum of understanding to purchase up to 50 wide-body aircraft during the Farnborough International Airshow at Farnborough Airport in the U.K., Monday (local time). Courtesy of Korean Air

Korean Air signed a memorandum of understanding (MOU) with Boeing in the U.K. on Monday (local time), marking a significant commitment to expand its fleet with the purchase of 20 Boeing 777-9 aircraft and 20 Boeing 787-10 Dreamliners, with an option to purchase 10 more of the largest variant of the 787 Dreamliner in the future, the airline said on Monday.

The size of the MOU is estimated to be worth around 30 trillion won ($22 billion).

The carrier explained that its latest agreement with the U.S. aircraft maker is intended to upgrade and expand its wide-body fleet.

With their capability of long-haul flights to regions such as North America and Europe, the 777-9 and 787-10 are also expected to play an important role after Korean Air's acquisition of Asiana Airlines.

"The addition of the Boeing 777-9 and 787-10 aircraft marks a significant milestone in our strategic objective to expand and upgrade our fleet," said Korean Air Chairman Cho Won-tae, who is also known by his English name, Walter Cho.

"This investment underscores our commitment to providing a best-in-class flying experience. These new airplanes will elevate passenger comfort and enhance operational efficiency, while significantly reducing carbon emissions, supporting our long-term commitment to sustainable aviation."

Korean Air's Boeing 787-10 aircraft, above, and the Boeing 777-9 / Courtesy of Korean Air

The 777-9 has new carbon-fiber composite wings, which are longer than those of the previous 777 family of airplanes, resulting in more than a 10 percent improvement in fuel efficiency.

With a range of over 13,000 kilometers, the aircraft can provide direct services to all U.S. destinations from Incheon International Airport. It also has the longest fuselage in the 777 series, with a typical seating capacity of 400 to 420 seats.

The 787-10 is the largest variant in the 787 family, capable of carrying 15 percent more passengers and cargo than the 787-9 currently in service. Compared to similar-sized aircraft, the Boeing 787-10 offers superior fuel efficiency with a reduction in carbon emissions of over 20 percent.

"We are honored Korean Air has selected two of our largest, most efficient wide-body airplanes to add capacity to their global network," said Stephanie Pope, president and CEO of Boeing Commercial Airplanes.

"Boeing airplanes have played an integral role in the growth of Korean Air over the past 50 years, and we are confident the 777X and 787 Dreamliner will support the airline's long-term sustainability goals and continued growth."

With the addition of the Boeing 777-9 and 787-10, Korean Air will have a total of 203 next-generation, eco-friendly aircraft in its fleet by 2034.