Southwest Airlines, the giant US low-cost carrier has ordered up to 255 Boeing 737 MAX aircraft - made up of 100 firm orders and 155 options. Southwest said that it had completed the multi-year evaluation of the successor aircraft to its Boeing 737-700 model, with the selection of the Boeing 737 MAX 7 aircraft. The first 30 are scheduled to be delivered in 2022. As part of the agreement, Southwest also converted 70 MAX 8 firm orders to MAX 7 firm orders and added 155 MAX options for MAX 7 or MAX 8 aircraft for the years 2022 through 2029. The airline says that these order book additions and revisions result in a new total of 349 MAX firm orders (200 MAX 7 and 149 MAX 8) and 270 MAX options for MAX 7 or MAX 8 aircraft for the years 2021 through 2031. Southwest says it expects delivery of 28 MAX 8 aircraft in total this year (19 from Boeing and 9 from third-party lessors), as well as 17 737-700 retirements, ending 2021 with 69 MAX 8 aircraft and 729 total aircraft. Southwest said that today's announcement "reinforces the Company's confidence in the 737 MAX as the future of the Southwest fleet. This cost-effective order book with Boeing allows the Company to maintain the operational efficiencies of an all-Boeing 737 fleet to support its low-cost, point-to-point route network." The airline was the launch customer of the MAX 8 and is scheduled to be the launch Customer of the MAX 7 after also launching prior 737 generations, including the -300, -500, and -700 series. "Southwest Airlines has been operating the Boeing 737 series for nearly 50 years, and the aircraft has made significant contributions to our unparalleled success. Today's commitment to the 737 MAX solidifies our continued appreciation for the aircraft and confirms our plans to offer the Boeing 737 series of aircraft to our Employees and Customers for years to come," said Gary Kelly, Southwest's Chairman and Chief Executive Officer. "We are proud to continue our tradition of being the world's largest operator of an all-Boeing fleet." "The MAX aircraft, with CFM International's LEAP-1B engines, enable exceptional operational efficiencies such as a 14 percent lower rate of fuel burn that reduces carbon emissions, quieter engines which benefit the communities we serve, and excellent dispatch reliability to support our on-time operations," said Mike Van de Ven, Southwest's Chief Operating Officer. Stan Deal, president, and CEO of Boeing Commercial Airplanes said: "Southwest Airlines has long been a leader and bellwether for the airline industry and this order is a big vote of confidence for commercial air travel. "As vaccine distribution continues to pick-up, people are returning to the skies and fueling hopes for a full recovery and renewed growth across our industry. We are deeply honored by Southwest’s continuing trust in Boeing and the 737. Their fleet decision today brings more stability for our biggest commercial program and will ensure that our entire 737 family will be building new airplanes for Southwest for years to come.”