Singapore Airlines has signed a firm order with Boeing for twenty 777-9s and nineteen 787-10s after settling on plans for fleet growth and route development over the next decade, the airline announced Monday. The signing took place at the White House in Washington D.C., during a ceremony witnessed by U.S. President Donald Trump and Singapore Prime Minister Lee Hsien Loong. It marked the finalization of an agreement announced in February as a letter of intent.

Along with the firm orders for 39 airplanes, SIA also took options for six more airplanes of each model. Boeing values the firm orders at $13.8 billion based on list prices.

SIA said it plans to use the 777-9s for long-haul routes. It expects delivery of the new widebodies starting in its 2021/2022 fiscal year. It expects to use the 787-10s on medium-range routes, primarily in Asia. Those airplanes come due for delivery starting in SIA’s 2020/2021 fiscal year.

SIA became the launch customer for the 787-10 in 2013, when it placed an order for 30. It plans to become the first operator of the type when it takes the first production 787-10 in the first half of next year.

Boeing rolled out the first Rolls-Royce Trent 1000-equipped 787-10 built for Singapore at its final assembly facility in North Charleston, South Carolina, in early October.

A straightforward 18-foot stretch of the 787-9, the 787-10 retains 95 percent design and build commonality with its smaller sibling while adding some 40 seats in exchange for range. Boeing lists the 330-seat 787-10’s range at 6,430 nautical miles, while the 787-9 operates to a range of 8,500 nautical miles. A pair of Rolls-Royce Trent 1000-10s powered the first 787-10 test airplane on its maiden flight in March. The company also offers General Electric GEnx turbofans for the biggest Dreamliner.

At Boeing’s main widebody plant in Everett, Washington, the 777-9 remains on schedule to reach completion of final engineering definition by the end of the year as program managers eye final assembly of the static test airframe in 2018. Featuring 105,000-pound-thrust GE9X turbofans and structural improvements to the fuselage that will allow for a 6,000-foot cabin altitude, the airplane appears well positioned to meet Boeing’s 2020 entry-into-service target, as the company progresses beyond pre-production verification and into full-scale production of its all-new composite wing.