Boeing [NYSE:BA] and United Airlines today announced the carrier will expand its 737 order book by purchasing an additional 200 737 MAX jets, including 150 for the largest member of the family, the 737-10, and 50 for the airplane that serves the heart of the single-aisle market, the 737-8. The new purchase positions United’s fleet for growth and accelerating demand for air travel.

“Our ‘United Next’ vision will revolutionize the experience of flying United as we accelerate our business to meet a resurgence in air travel,” said United CEO Scott Kirby. “By adding and upgrading this many aircraft so quickly with our new signature interiors, we’ll combine friendly, helpful service with the best experience in the sky, all across our premier global network. At the same time, this move underscores the critical role United plays in fueling the broader U.S. economy – we expect the addition of these new aircraft will have a significant economic impact on the communities we serve in terms of job creation, traveler spending and the shipping of goods and services.”

The purchase increases United’s order book for the fuel-efficient, single-aisle family to 380 airplanes, excluding 30 that have been delivered. As the launch customer for the 737-10, United placed its first order in 2017 by converting 100 737-9 orders to the larger 737-10 variant. Today’s agreement also includes the purchase of Boeing 737 MAX training simulator data packages to support United’s pilot training programs.

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Designed and built in Renton, Washington, the 737 MAX family delivers superior efficiency, flexibility and reliability while reducing fuel use and carbon emissions by at least 14% compared to the airplanes it replaces. The 737-8 seats up to 189 passengers and can fly 3,550 nautical miles – about 600 miles farther than its predecessor – allowing airlines to offer new and more direct routes for passengers.

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The largest model in the family, the 737-10 seats up to 230 passengers in a single-class configuration and can fly up to 3,300 miles. The fuel-efficient jet can cover 99% of single-aisle routes, including routes served by 757s.