Boeing 737 MAX
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 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 8-200, launched by Ryanair. The aircraft typically seats 138 to 204 passengers in a two-class configuration and has a range of., Boeing has delivered 2,120 aircraft and held orders for 4,853 more. The MAX 8 is the most widely ordered variant, while the MAX 7 and MAX 10 have not yet received FAA certification, and the agency has not provided a timeline for their 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, 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.
Development
Background
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, 130 A320neo, and 100 737NG. Officials also said they would order 100 re-engined 737s with CFM LEAP if Boeing pursued the project.
Program launch
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, 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 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, and closer to. 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.
Production
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 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 , followed by the engines at , systems and interiors at each, then avionics at .
Flight testing and certification
The 737 MAX gained its airworthiness approval based on the 737 legacy series, as a Supplemental type certificate, in lieu of a new design approval. The MAX's first flight took place on January 29, 2016, at Renton Municipal Airport, nearly 49 years after the maiden flight of the original 737-100, on April 9, 1967. The first MAX 8, 1A001, was used for aerodynamic trials: flutter testing, stability and control, and takeoff performance-data verification, before it was modified for an operator and delivered. 1A002 was used for performance and engine testing: climb and landing performance, crosswind, noise, cold weather, high altitude, fuel burn and water-ingestion. Aircraft systems including autoland were tested with 1A003. 1A004, with an airliner layout, flew function-and-reliability certification for 300 hours with a light flight-test instrumentation.
The 737 MAX 8 gained FAA certification on March 8, 2017, and in the same month was approved by the European Union Aviation Safety Agency on March 27, 2017. After completing 2,000 test flight hours and 180-minute ETOPS testing requiring 3,000 simulated flight cycles in April 2017, CFM International notified Boeing of a possible manufacturing quality issue with low pressure turbine discs in LEAP-1B engines. Boeing suspended 737 MAX flights on May 4, and resumed flights on May 12.
During the certification process, the FAA delegated many evaluations to Boeing, allowing the manufacturer to review its own product. It was widely reported that Boeing pushed to expedite approval of the 737 MAX to compete with the Airbus A320neo, which hit the market nine months ahead of Boeing's model.
Entry into service
The first delivery was a MAX 8 on May 16, 2017, to the then Malindo Air ; it entered service on May 22. Norwegian Air International was the second airline to put a 737 MAX into service, when it performed its first transatlantic flight with a MAX 8 named Sir Freddie Laker on July 15, 2017, between Edinburgh Airport in Scotland and Bradley International Airport in the U.S. state of Connecticut.Boeing aimed for 737 MAX to match the 99.7% dispatch reliability of the 737 Next Generation. Southwest Airlines, the launch customer, took delivery of its first on August 29, 2017. Boeing planned to deliver at least to aircraft in 2017, 10–15% of the more than five hundred 737s to be delivered in the year.