Singapore Airlines (SIA) has finalised a $13.8bn order with Boeing to purchase 39 aircraft, comprising 20 777-9s and 19 787-10 Dreamliners.

The deal also includes six options for each aircraft type, which is set to expand the order to 51 aircraft if exercised.

A letter of intent for the newly finalised deal was signed in February, with the aim of modernising SIA’s fleet and grow its network through the next decade.

SIA aims to serve long-haul routes with the new 777-9 aircraft, the delivery of which are expected to begin from the 2021/2022 financial year.

“These new aircraft will also provide the SIA Group with new growth opportunities.”

The airline’s new 787-10 aircraft will be operated on medium-range routes and are scheduled for delivery from the 2020/2021 fiscal.

SIA CEO Goh Choon Phong said: “SIA has been a Boeing customer for many decades and we are pleased to have finalised this major order for wide-body aircraft, which will enable us to continue operating a modern and fuel-efficient fleet.

“These new aircraft will also provide the SIA Group with new growth opportunities, allowing us to expand our network and offer even more travel options for our customers.”

The airline also expects to take delivery of the world’s first Boeing 787-10 by the first half of next year. The delivery will take place as part of an order announced in 2013 for 30 Boeing aircraft.

SIA currently operates more than 50 units of current-generation Boeing 777 aircraft.

Various subsidiaries of the airline, including SilkAir, Scoot and SIA Cargo, also operate a number of Boeing aircraft, 737 MAX 8 and 737-800, 787-8/9 and 747-400 Freighter, respectively.