The nation's flagship carrier Korean Air is set to purchase Boeing's state-of-the-art mid- to large-sized aircraft, the 777-9 and 787-10, as part of its modernization initiative.

According to the airline, it signed a memorandum of understanding(MOU) on the purchase of up to 50 Boeing aircraft on Monday, during the Farnborough International Airshow in the United Kingdom.

The agreement, reported to be worth around 30 trillion won, or around 22 billion U.S. dollars, is the biggest aircraft purchase deal Korean Air has signed to date.

The 777-9 has a fuel efficiency that's over ten-percent higher than other 777-class aircraft, and can travel more than 13-thousand kilometers, while accommodating up to 420 passengers.

The 787-10 can transport an additional 15 percent of passengers and freight compared to the 787-9 currently in operation, with 25-percent higher fuel efficiency compared to the existing 777-200.