United Continental Holdings Inc. ordered nine Boeing Co. 787-9 wide-body jets valued at more than $2.5 billion, bolstering its bet on the Dreamliner to refresh its long-haul fleet.

Delivery of the new planes is expected to begin in 2020, the Chicago-based carrier said in a statement Monday. United plans to have 40 Dreamliners in its fleet by year’s end, with an additional two dozen on order.

The purchase will enable United to fly more 787-9s on some of its longest nonstop routes—such as Houston to Sydney and San Francisco to Singapore—replacing older, less-fuel-efficient planes like the Boeing 777. The deal’s value is based on list prices, although large airlines typically receive steep discounts.

The order boosts United’s bet on the Dreamliner, Boeing’s most advanced plane. United also said it will begin flying the new 787-10 on Jan. 7, becoming the first North American carrier to operate the latest, and longest, version in the Dreamliner family. The -10 is 18 feet longer than the 787-9. which has the longest range among Dreamliners, at 7,635 nautical miles.

The -10 initially will fly on two of United’s 12 daily routes to Los Angeles from its Newark, New Jersey, hub, and on one daily flight to San Francisco from Newark. The airline plans to shift some of the planes onto European routes starting next summer, according to United’s pilots union. The -10 is the largest of Boeing’s three Dreamliners, carrying about 330 passengers in a two-class configuration.

United was little changed at $88.85 at 12:44 p.m. in New York. The stock had gained 32 percent this year through Sept. 28. Boeing climbed 2.1% to $379.79, after advancing 26 percent for this year.