Singapore Airlines has formally signed a firm order with Boeing for 20 777-9s and 19 787-10s during a visit by Lee Hsien Loong, prime minister of Singapore, to Donald Trump, president of the United States, at the White House in Washington DC.

The signing finalizes an agreement which was announced in February 2017 as a letter of intent. The deal also includes six options for each aircraft type.

“SIA has been a Boeing customer for many decades and we are pleased to have finalised this major order for widebody aircraft, which will enable us to continue operating a modern and fuel-efficient fleet,” said Goh Choon Phong, CEO of Singapore Airlines. “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 777-9s are intended primarily for long-haul routes and are due for delivery from the 2021-22 financial year. The 787-10s will be deployed on medium-range routes and are due for delivery from the 2020-21 financial year.

Singapore Airlines is the launch customer of the 787-10 and already had 30 on order from a deal signed in 2013. With 49 now on order, it becomes the largest customer for the type.

“Boeing and Singapore Airlines have been strong partners since the airline’s first operations 70 years ago and we are thrilled to finalize their purchase of 20 777Xs and 19 additional 787-10 Dreamliners,” said Kevin McAllister, president and CEO of Boeing Commercial Airplanes. “Singapore Airlines’ order is a testament to the market-leading capabilities of Boeing’s widebody airplanes and we look forward to delivering the very first 787-10 to them next year.”

Singapore Airlines’ current fleet consists of more than 50 current-generation 777 aircraft, and subsidiaries SilkAir, SIA Cargo and Scoot also operate 737-800s, 737 MAX 8s, 747-400Fs, 787-8s and 787-9s.