Singapore Airlines (SIA) announced Thursday an order for a total of 39 Boeing passenger planes worth $13.8 billion as part of its growth plans for the next decade.

The carrier said in a statement that it had signed a letter of intent with the US manufacturer for 20 777-9s and 19 787-10s, with options for six more of each aircraft, bringing the total to 51 if exercised.

"Today’s major order for widebody aircraft enables us to continue operating a modern and fuel-efficient fleet, providing the SIA Group with additional expansion opportunities to ensure that we retain our industry-leading position," chief executive Goh Choon Phong said in a statement.