Airbus A350-1000 / Courtesy of Korean Air

Korean Air will sign a contract with Airbus for the procurement of 33 state-of-the-art A350 family of aircraft, the airline said Thursday.

Under the deal, the nation's flag carrier will purchase 27 A350-1000s and six A350-900s. The contract is worth $13.7 billion (18.17 trillion won).

The order will supplement the airline's long-term fleet operations, as it gradually retires older aircraft. The procurement of the next-generation, eco-friendly A350 passenger planes is not only aligned with the carrier's sustainability efforts, but is also seen as part of preparatory steps for the integration of Asiana Airlines, according to Korean Air.

The A350-1000 is the largest in the A350 family and can accommodate 350 to 410 passengers in a standard three-class configuration. The aircraft makes use of advanced composite materials, which help reduce fuel consumption and carbon emissions by up to 25 percent compared to similarly-sized previous aircraft models.

With the longest flight range among existing passenger aircraft, the A350-1000 can operate up to 16,000 kilometers with a full payload.

The A350-900 variant is about seven meters shorter than the A350-1000 with a range of 15,370 kilometers. The airline can deploy the aircraft on long-haul routes, such as Incheon to New York, where it currently operates two daily flights.

Korean Air also plans to introduce 50 Airbus A321neos, 10 Boeing 787-9s, 20 Boeing 787-10s, and 30 Boeing 737-8s. The airline said it will continue to prioritize fleet modernization and reduction of carbon emissions through the operation of new aircraft and other sustainability activities.