The Boeing 737 MAX is a series of narrow-body aircraft developed by Boeing Commercial Airplanes as the fourth generation of the Boeing 737. It succeeds the Boeing 737 Next Generation and incorporates more efficient CFM International LEAP engines, aerodynamic improvements such as split-tip winglets, and structural modifications. The program was announced in August 2011, the first flight took place in January 2016, and the aircraft was certified by the U.S. Federal Aviation Administration (FAA) in March 2017. The first delivery, a MAX 8, was made to Malindo Air in May 2017.
The 737 MAX series includes four main variants—the MAX 7, MAX 8, MAX 9, and MAX 10—with increasing fuselage length and seating capacity. Boeing also developed a high-density version, the MAX 200, launched by Ryanair. The aircraft typically seats 138 to 204 passengers in a two-class configuration and has a range of 3,300 to 3,850 nautical miles [nmi] (6,110 to 7,130 km; 3,800 to 4,430 mi). As of June 2026, Boeing has delivered 2,360 aircraft and held orders for 4,846 more. The MAX 8 is the most widely ordered variant, while the MAX 10 has not yet received FAA certification, and the agency has not provided a timeline for its approval. Its primary competitor is the Airbus A320neo family, which occupies a similar market segment.
Two fatal accidents, Lion Air Flight 610 in October 2018 and Ethiopian Airlines Flight 302 in March 2019, led to the global grounding of the 737 MAX fleet from March 2019 to November 2020. The crashes were linked to the Maneuvering Characteristics Augmentation System (MCAS), which activated erroneously due to faulty angle of attack sensor data. Investigations revealed that Boeing had not adequately disclosed MCAS to operators and identified shortcomings in the FAA's certification process. The incidents caused significant reputational and financial damage to Boeing, including billions of dollars in legal settlements, fines, and cancelled orders.
Following modifications to the flight control software and revised pilot training protocols, the aircraft was cleared to return to service. By late 2021, most countries had lifted their grounding orders. However, the type came under renewed scrutiny after a January 2024 incident in which a door plug detached mid-flight on Alaska Airlines Flight 1282, causing a rapid decompression. The FAA temporarily grounded affected MAX 9 aircraft, and investigations raised further concerns about production quality and safety practices at Boeing.
In 2006, Boeing began to consider replacing the 737 with a "clean sheet" design that could follow the Boeing 787 Dreamliner. In June 2010, executives postponed the decision. On December 1, 2010, Boeing competitor Airbus launched the Airbus A320neo family, which offered better fuel economy and operating efficiency than the 737 NG, thanks to its engines: the LEAP from CFM International and the PW1000G from Pratt & Whitney.
In February 2011, Boeing CEO Jim McNerney said, "We're going to do a new airplane." The company had been developing a new aircraft to replace the 737 as part of its Yellowstone Project. In March 2011, Boeing CFO James A. Bell told investors that the company might re-engine the 737, but later that month Boeing Commercial Airplanes President James Albaugh said that the company was not sure about that. The Airbus A320neo gathered 667 commitments at the June 2011 Paris Air Show, bringing its order backlog to 1,029 aircraft, an order record for a new commercial airliner.
On July 20, 2011, American Airlines, which had long bought only Boeing jets, announced an order for 460 narrowbody jets including 130 A320ceo (current engine option), 130 A320neo, and 100 737NG. Officials also said they would order 100 re-engined 737s with CFM LEAP if Boeing pursued the project.
Faced with the record orders for Airbus and the defection of a long-time customer, on August 30, 2011, Boeing's board of directors approved the launch of the re-engined 737 MAX, which they said would meet or exceed the range of the Airbus A320neo while burning 4% less fuel. Studies for additional drag reduction were performed during 2011, including revised tail cone, natural laminar flow engine nacelle, and hybrid laminar flow vertical stabilizer. To focus on the re-engine project, Boeing abandoned the development of a new design under its Yellowstone Project. Firm configuration for the 737 MAX was scheduled for 2013.
In March 2010, the estimated cost to re-engine the 737, according to Mike Bair, Boeing Commercial Airplanes' vice president of business strategy and marketing, would be US$2–3 billion, including the CFM engine development. During Boeing's Q2 2011 earnings call, CFO James Bell said the development cost for the airframe only would be 10–15% of the cost of a new program, which was estimated at US$10–12 billion at the time. Bernstein Research predicted in January 2012, that this cost would be twice that of the A320neo. The MAX development cost could have been well over the internal target of US$2 billion, and closer to US$4 billion. Fuel consumption is reduced by 14% from the 737NG. Southwest Airlines was signed up as the launch customer in 2011.
In November 2014, McNerney said the 737 would be replaced by a new airplane by 2030—probably using composite materials—that would be slightly bigger and have new engines but would retain the 737's general configuration. Boeing talked about developing a clean sheet aircraft to replace the 737. The conceived aircraft was to have a fuselage similar to the 737 though slightly larger, and would make use of the advanced composite technology developed for the 787 Dreamliner. Boeing also considered a parallel development along with the 757 replacement, similar to the development of the 757 and 767 in the 1970s.
On August 13, 2015, the first 737 MAX fuselage completed assembly at Spirit Aerosystems in Wichita, Kansas, for a test aircraft that would eventually be delivered to launch customer Southwest Airlines. On December 8, 2015, the first 737 MAX—a MAX 8 named Spirit of Renton—was rolled out at the Boeing Renton Factory.
Because GKN could not produce the titanium honeycomb inner walls for the thrust reversers quickly enough, Boeing switched to a composite part produced by Spirit to deliver 47 MAXs per month in 2017. Spirit supplies 69% of the 737 airframe, including the fuselage, thrust reverser, engine pylons, nacelles, and wing leading edges.
A new spar-assembly line with robotic drilling machines was expected to increase throughput by 33%. The Electroimpact automated panel assembly line sped up the wing lower-skin assembly by 35%. Boeing planned to increase its 737 MAX monthly production rate from 42 planes in 2017, to 57 planes by 2019. The new spar-assembly line is designed by Electroimpact. Electroimpact has also installed fully automated riveting machines and tooling to fasten stringers to the wing skin.
The rate increase strained the production and by August 2018, over 40 unfinished jets were parked in Renton, awaiting parts or engine installation, as CFM Leap-1B engines and Spirit fuselages were delivered late. After parked airplanes peaked at 53 at the beginning of September, Boeing reduced this by nine the following month, as deliveries rose to 61 from 29 in July and 48 in August.
On September 23, 2015, Boeing announced a collaboration with Comac (Commercial Aircraft Corporation of China) to build a completion and delivery facility for the 737, in Zhoushan, China, the first outside the United States. This facility initially handles interior finishing only, but will subsequently be expanded to include paintwork. The first aircraft was delivered from the facility to Air China on December 15, 2018.
The largest part of the suppliers cost are the aerostructures at US$10–12 million (35-34% of the US$28.5−35 million total), followed by the engines at US$7−9 million (25-26%), systems and interiors at US$5–6 million each (18-17%), then avionics at US$1.5–2 million (5-6%).
In July 2026, Boeing started assembling 737 MAXs at a new production line at the existing widebody factory in Everett, Washington. This fourth production line is planned to increase total monthly output to 52 planes when it reaches full capacity. The line, formerly used for much larger 787s, has more space than Renton and can produce the largest 737 MAX 10 variant without restrictions, unlike the more space-limited Renton lines, where 737 MAX 10s must be interspersed with smaller 737 MAX 8s to fit on the line.