Everything You Wanted to Know About the Boeing 737 MAX
If you've ever wanted to know more about the Boeing 737 MAX, look no further. In this article, we'll cover everything you need to know about the MAX series.
If you've ever wanted to know more about the Boeing 737 MAX, look no further. In this article, we'll cover everything you need to know about the MAX series.
DALLAS — The Boeing 737 MAX has been at the center of one of the biggest crises in aviation history, following two fatal crashes that resulted in the grounding of the entire fleet. Despite this, the 737 MAX remains one of the most popular aircraft in the world, with a rich history and a vast network of operators and suppliers.
The Boeing 737 MAX series is the fourth generation of the manufacturer's narrowbody 737 airliner family. The MAX includes new engines and other improvements in comparison to the company’s Next-Generation (NG) 737 series. The single-aisle market benefits from the Boeing 737 MAX's increased efficiency, improved environmental performance, and increased passenger comfort.
The type delivers outstanding economics, decreasing fuel use and pollutants by 20% while producing a 50% smaller noise footprint than the aircraft it replaces. It also has cutting-edge winglets and effective engines. When compared to its rivals, the 737 MAX delivers up to 14% cheaper airframe maintenance costs.
The Boeing 737 MAX series was introduced in December 2011 after receiving an order from Southwest Airlines. A Boeing 737-8 with the serial number 42554 and the registration N8701Q made the series' inaugural flight on January 29, 2016, from Renton Field in Washington state. The 737-8 was certified by the FAA on March 8, 2017, following a nearly 14-month flight-testing procedure.
Boeing announced the fifth variant of the MAX series, the 737-10, at the 2017 Paris Air Show, a variant that is designed to directly compete with Airbus’s A321neo (new engine option). When it was launched in June 2017, the 737-10 had orders for 240 airplanes from operators and leasing companies.
This included AerCap, Aviation Capital Group (ACG), Copa Airlines, Donghai Airlines, GE Capital Aviation Services, Lion Air, Malaysian Airlines, TUI Group, United Airlines, and Xiamen Airlines.
Boeing subsequently rolled out the first 737-10 airframe—Serial No. 66122, registered as N27751—at Renton in November 2019, with the first flight occurring on June 18, 2021. At the time of the variant’s first flight, Boeing stated that it expected this 737 MAX airframe to enter into service in 2023.
The type certificate for all variants of the 737 series—from the -100 to the -9—is held by The Boeing Company of Renton, Washington.
737 MAX VariantFAA Certification Date737-8March 8, 2017737-9Feb. 15, 2018737-8200 (737-8-200)March 31, 2021Series Configuration range
The 737-7, which is intended to have a maximum seating capacity of 172, is at the low end of the MAX series capacity range. This capacity is feasible in a single-class cabin with seats that have a 28- or 29-inch pitch. The -7's dual-class seating capacity is decreased to 138–153 people, with the higher end of that range being feasible in a configuration that comprises eight business-class seats with a 36-in. pitch and 145 economy-class seats with a 29–30.
Boeing claims that the 737-8's 189-passenger maximum capacity is feasible in a single-class cabin with seats that have a 29- or 30-inch pitch. The -8 can accommodate 162-178 passengers in a two-class arrangement, and the -9 can accommodate 178–193 passengers.
12 of the 178 passengers may be accommodated in business class seats with a 36-inch pitch, while the remaining 166 seats would be located in the economy cabin, which would have seats with a pitch of either 29 or 30 inches.
This is one conceivable layout for a 178-passenger dual-class -8. The 737-8-200 is the higher-capacity version of the 737-8 and may be configured with 200 seats, each with a 28-inch pitch.
737 MAX vs. 737NG Seating ComparisonMAX VariantMaximum Certified Passenger CapacityNG VariantMaximum Certified Passenger Capacity737-7 (737 MAX 7)172737-700149737-8 (737 MAX 8)189737-800189737 8200 (737-8-200)212737-900ER220737-9 (737 MAX 9)220737-10 (737 MAX 10)230Seating Comparison between 737MAX vs 737NG
The -9 and -10, which have maximum passenger capacities of 220 and 230, respectively, are the highest capacity variants of the 737 MAX series. Similar to the -7 and -8, the -9's single-class layout is capable of accommodating those maximum capacities, with seats in a such arrangement having a 28-inch pitch.
The -9's interior includes 177 economy-class seats with a 29- or 30-inch pitch and 16 business-class seats with a 36-inch pitch, and it can accommodate the high end of the dual-class seating range discussed earlier.
Two cargo compartments, labeled forward and aft, offer extra space in addition to the cabin's usable space. For the 737-7, those compartments' respective bulk volumes are 433 and 706, for a combined 1,139 ft3 of bulk cargo volume. The total space increases to 1,540 ft3, divided between 657 ft3 in the front cabin and 883 ft3 in the aft compartment on the 737-8 and -8-200.
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The -9 sees an increase in those volumes, with a total volume of 1,811 ft.3 indicated in Boeing's airport planning document, with 815 ft.3 of that space located in the front compartment and 996 ft.3 in the aft compartment.
The 737-10, as anticipated, will feature the largest combined bulk cargo volume of 1,961 ft.3, with 911 ft.3 of that space being held in the forward compartment and the remaining 1,050 ft.3 being located in the rear compartment.
The avionics system also improved, and flight crews now fly variations of the MAX series—from a flight deck equipped with Collins Aerospace displays.
The 737 MAX series is marketed by Boeing as "building" on the dependability of the 737NG versions and offering notable enhancements in emissions, operating costs, and performance.
Despite parallels to the 737 airframes from earlier generations, the Airbus' A320neo family serves as the main rival for the 737 MAX series, with the specific comparisons given below.
Comparison: A320neo and 737 MAX SpecificationsA319neoA320neoA321XLR737-7737-8/8-200737-9737-10Maximum Certified Passenger Capacity160195244172189/212220230Maximum Range (nm)3,7003,4004,7003,8503,5503,300EngineCFM International LEAP-1ACFM International LEAP-1BPratt & Whitney PW1100G-JMMaximum Takeoff Weight (MTOW)(lb.)166,449174,165222,667177,000182,200/181,200194,700197,900Wingspan117 ft. 5 in.117 ft. 10 in.Length111 ft.123 ft. 3 in.146 ft.116 ft. 8 in.129 ft. 8 in.138 ft. 2 in.143 ft. 8 in.Height38 ft. 7 in.40 ft. 4 in. Performance specifications
The 737NG series—the -600, -700, -700C, -800, -900, and -900ER—and the 737-8 and -9 share additional characteristics, such as a maximum operating limit speed (MMO) of 0.82 Mach and a maximum operating altitude of 41,000 ft.
The values for the -9 and -10 are based on the range estimates for the MAX mentioned above and below, which assume an airframe with a single auxiliary fuel tank. Moreover, even though the -8 and -9 are both touted as having the same 3,550-nm range, the earlier model can reach that range without an additional fuel tank.
The 737-7 will have 1,000 nm more range than the 737-700 thanks to the "technological enhancements" built into that airframe, and it will also be able to transport more passengers. The bigger -8, according to Boeing, has a range that is 14% longer than "the latest 737-800" when using the same amount of fuel.
Changes that are shared by all four 737 MAX variants include an increased wingspan—to 117 ft. 10 in., and the "dual-surface, laminar-flow winglets provide 2% over the blended winglets fitted to" 737NG airframes, even if the LEAP-1B engines "mostly" enable the range boost.
The 737-7, the smallest model in the 737 MAX series, is the model that has the longest range and is produced by Boeing in Renton. The fuselage of the -7 was stretched by 76 inches to accommodate two additional rows of seats, resulting in the addition of 12 more seats compared to the 737-700 in response to comments from -7 customers Southwest Airlines and WestJet Airlines.
In addition to having a longer fuselage, the revised -7 design increases range, improves performance in hot and high-altitude circumstances and increases maximum takeoff weight (MTOW) by 6,000 pounds over the 737-700's increased-gross-weight (IGW) model.
Fuel expenses for the -7 are 18% lower per seat than for the -700 of the previous generation, which is another advancement. Moreover, Boeing claims that the -7 can travel "12 more passengers 400 nm further" than the A319neo while having operating expenses that are 7% lower per seat.
Similar to the -800 variant, the MTOW of the 737-8 is enhanced by 7,000 lb. while maintaining a fuselage length that is almost comparable. Boeing claims that the -8's fuselage is 6 ft. 5 in. longer than that of its main rival, the A320neo, giving operators greater room and flexibility in the cabin.
The inclusion of the mid-exit door of the -9, which "increases the exit limit," allows for the enhanced capacity of the 737-8-200 (737 MAX 200), an aircraft that is said to be built on the 737-8. In addition, it is claimed that the MAX 200 has 20% greater fuel efficiency per seat than "today's most efficient single-aisle airplanes"
The longer fuselage of the -9 allows for the installation of three more rows of seats compared to the 737-8. The main landing gear of the -10 is extended by 9.5 in. in order to provide "sufficient clearance of the longer body for rotation" during takeoff and landing, adding to the 8-in. extension of the MAX's nose gear that was necessary to allow proper ground clearance for the LEAP engines.
To "ensure the airplane remains stall—rather than pitch—limited" was also included. The main landing gear's increased height does indeed enable the fuselage to extend, and the design also enables the larger landing gear to fit "within the existing wheel well area."
Further alterations to the -10 include a "lighter flat aft pressure bulkhead," a "variable exit-limit rating mid-exit door," and a wing that was altered for "low-speed drag reduction" in addition to the lengthened fuselage and changes to the main landing gear to accommodate it.
Comparison: 737NG and 737 MAX SpecificationsType737-700737-800737-900ER737-7737-8/-8-200737-9737-10Commercial Designation737 MAX 7737 MAX 8/737 MAX 200737 MAX 9737 MAX 10Maximum Certified Passenger Capacity149189220172189/212220230Maximum Range (nm)3,0102,9352,9503,8503,5503,300EngineCFM International CFM56-7BCFM International LEAP-1BMaximum Takeoff Weight (MTOW)(lb.)154,500174,200187,700177,000182,200/181,200194,700197,900171,000 (IGW)Maximum Landing Weight (lb.)129,200146,300157,300145,600152,800163,900167,400134,000 (IGW)Usable Fuel Capacity (gal.)6,820Wingspan117 ft. 5 in.117 ft. 10 in.Length110 ft. 4 in.129 ft. 6 in.138 ft. 2 in.116 ft. 8 in.129 ft. 8 in.138 ft. 2 in.143 ft. 8 in.Height41 ft. 3 in.40 ft. 4 in.
All airframes in the MAX series are powered by LEAP-1B engines made by CFM International, replacing the CFM56. The improvements provided by the LEAP engines include a reduction in fuel consumption—which, according to CFM, is 15% better when compared to “today’s best CFM56 engines”—and emissions, while retaining the “life-cycle maintenance costs” and reliability of the CFM56.
Specific emissions reductions made possible by the LEAP include a 50% reduction in nitrogen oxide (NOX) emissions in comparison to the Committee on Aviation Environmental Protection’s CAEP/6 standards. CFM states that reduction is made possible through the inclusion of a “second-generation” Twin-Annular, Pre-Mixing Swirler Combustor (TAPS II), a type of combustor that “pre-mixes” fuel and air prior to combustion.
The engine’s FAA TCDS notes that in addition to the TAPS II combustors, the variants of the LEAP-1B—which are high-bypass turbofan engines—have a multi-stage low-pressure turbine and compressor, as well as a two-stage high-pressure turbine. Driving the coaxial front fan/booster of the LEAP-1B is the multi-stage low-pressure turbine, while the engine itself incorporates a full authority digital engine control (FADEC) system.
Other technologies incorporated into the LEAP engine series include fan blades that are “manufactured from 3D-woven RTM (resin transfer molding) carbon-fiber composite,” a technology that decreases weight and increases durability. When compared to conventionally manufactured parts, the LEAP’s fuel nozzles are “five times more durable,” while also being “25% lighter than previous models.”
Despite incorporating those advanced materials, the increase in the size of the LEAP-1B in comparison to the CFM56—the LEAP-1B’s 18-blade carbon-fiber fan has a 69.4-in. diameter in comparison to the 61-in. diameter of the CFM56-7’s 24-blade titanium fan—means the total weight of the engine also increased to 6,128 lb.
737 MAX Series Engine Variants737 MAX VariantEngine Variant737 MAX VariantEngine Variant737-8/-8200CFM LEAP-1B25G05737-9CFM LEAP-1B27G05CFM LEAP-1B25G06CFM LEAP-1B27G06CFM LEAP-1B27G05CFM LEAP-1B28G05CFM LEAP-1B27G06CFM LEAP-1B28G06CFM LEAP-1B28G05CFM LEAP-1B28B1G05CFM LEAP-1B28G06CFM LEAP-1B28B1G06CFM LEAP-1B28B1G05CFM LEAP-1B28B1G06
Alaska Airlines, a Boeing and MAX customer, stated on June 3, 2021, that an Alaska 737-9 would be used as part of the airframe manufacturer's ecoDemonstrator program to "flight test roughly 20 innovations" with the aim of enhancing both the sustainability and safety of operations.
The usage of recycled carbon composite material in the cabin sidewall panels—material that was sourced from the manufacturing of the 777X's wings—will be tested during those tests, which the firms stated would last five months.
The -9-based ecoDemonstrator will also test a fire-extinguishing agent that is meant to replace Halon 1301—the production of which “was banned in 1994”—with the goal of lowering the impact of the agent on the ozone layer substantially.
All Boeing 737 MAX versions are made at Boeing's factories in Renton, Washington. The 737-8 program used four test airframes for flight testing, compared to two each for the -7 and -9 programs.
Following the 737-8 and -9's entrance into service, three MAX series variants—the -7, -8-200, and -10—remain to be certified, with the first flights of the first two taking place in 2018 and early 2019, respectively.
The first of those mishaps happened on October 29, 2018, when a Lion Air 737-8 with the registration PK-LQP was lost around 13 minutes after taking off from Jakarta, Indonesia.
Less than five months later, on March 10, 2019, an Ethiopian Airlines -8 with the registration number ET-AVJ was involved in a second accident 6min. post takeoff.
Global aviation authorities gradually grounded the MAX fleet after the loss of the second MAX airframe and after initial intelligence showed similarities with the Lion Air catastrophe. A flight-control regulation known as Boeing as Maneuvering Characteristics Augmentation System was the subject of the accident investigations and the cause of the worldwide grounding of 737 MAX airframes (MCAS). In particular, at low speeds and steep angles of attack, the MCAS was "added in the 737 MAX to make it handle like a 737NG."
Following the disaster involving an Ethiopian Airlines 737-8 in March 2019, all MAX airframes were gradually stopped by aviation regulators. This process was started by the Civil Aviation Administration of China, which made the decision to halt MAX models on March 11. The following day, operations were prohibited by the Civil Aviation Safety Authority of Australia (CASA) and the Civil Aviation Authority of Singapore. On the same day, Indonesian authorities grounded aircraft used by Lion Air and Garuda Indonesia "for inspections" (March 12).
The European Union Aviation Safety Agency (EASA), which made the decision in reaction to the Ethiopian Airlines crash, also issued an airworthiness directive on March 12 that banned MAX operations throughout Europe. Finally, on March 13, Canada and the U.S. decided to halt MAX operations. As a result, airlines like WestJet, American Airlines, Air Canada, Southwest Airlines, and United Airlines were affected. Also, all MAX deliveries were stopped as a result of the grounding.
The flight-test program for the 737-7 resumed on May 15, 2019, following the use of the first -7 flight-test airframe—1E001—to carry out evaluations related to upgraded MCAS software, despite the uncertainty at the time regarding when Boeing would finish the changes and upgrades that would enable the 737 MAX series to return to service.
On Nov. 18, 2020, Boeing declared that the FAA had withdrawn its order halting "commercial operations" of the 737 MAX models that were certified at the time that order was issued, the -8 and -9, after additional testing that lasted more than 4,400 hours and 1,350 flights. In addition, it permitted Boeing to resume 737 variant deliveries, according to the company's press release announcing the event. "Airlines that are under the FAA's jurisdiction, including those in the U.S., can take the measures necessary to restore service," it stated.
However, a number of conditions must be satisfied before airlines governed by the FAA can resume scheduled service with 737 MAX variants. These conditions include "de-preservation activities" for stored airframes, adjustments to separate wiring, pilot training, and the installation of software updates for the flight computer. The airframe's MCAS is affected by the new software and the FAA-mandated training requirements, and the software updates include "changed logic."
The FAA lifted an order that prohibited the commercial operation of -8 airframes in that nation a week later, on Nov. 25, 2020, and the Brazilian National Civil Aviation Agency [Agencia Nacional de Aviacao Civil (ANAC)] followed suit. EASA announced on January 27, 2021, that it had approved the 737 MAX series' return to service, subject to many of the same requirements as the FAA—such as modifications to the wiring and maintenance of the airframe, as well as training and software upgrades—while Transport Canada's and Australia's CASA's suspension of operations were lifted on January 18, 2021, and February 26, 2021, respectively.
As the orders that had obstructed operations were gradually lifted in late 2020 and early 2021, Brazilian low-cost carrier Gol Airlines became the first user to relaunch the 737 MAX. A 737-8 was deployed to complete the journey from So Paulo to Porto Alegre. On a flight between Miami and New York LaGuardia on December 29, 2020, American Airlines formally inaugurated its services.
When Czech charter airline Smartwings operated a -8 between Prague and Malaga, Spain, on February 25, 2021, it became the first European carrier to use a 737 MAX airframe—nearly a month after EASA stated that it had authorized the series' return to operation. Boeing estimates that the first -10 deliveries will take place in 2023, following the initial shipments of the MAX 200 and -7 in early 2021.
After the MAX was put back into service, a problem with production line adjustments made in "early 2019" led to "electrical bonding and grounding difficulties" that affected more than 100 already-delivered airframes to operators. 350 "undelivered aircraft [that Boeing had in its inventory" also needed alterations, in addition to the changes that had to be made to the already-delivered aircraft. The business also made adjustments to the 737 MAX production line.
As of late March 2023, there were 954 active Boeing 737 MAX aircraft in airline fleets. This is up from around 580 the previous year. The 737-8 is by far the most dominant (with 711 of the active aircraft), followed by the larger -9 and the higher capacity -8200.
Southwest Airlines has long been the largest operator of the MAX, with 156 737-8 aircraft in the fleet. Ryanair is the second-largest operator, with 94 aircraft (all -8200 aircraft) across the group.
The top 12 operators of the 737 MAX are as follows:
Airline737-8737-8-200737-9TotalSouthwest156156Ryanair Group9494United Airlines405191Aeromexico311445flydubai41344American Airlines424242Alaska Airlines4141Air Canada3939GOL3737Turkish Airlines27532TUI Group3131WestJet22729
Aircraft deliveries were suspended during the grounding, but these have now been well resumed. Orders are back too. As of early March 2023, there remain over 4,000 unfilled 737 MAX aircraft (according to data from Boeing)
This includes some very large orders that will significantly change some airline fleets - including 409 aircraft for United Airlines, 372 aircraft for Southwest Airlines, 229 for Lion Air, 200 for VietJet Air, 125 for Jet Airways, 129 for Spice Air, 102 for Alaska Airlines, and 100 for Delta Air Lines.
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Featured image: Max Langley/Airways. References: Airways Archives, EASA TCDS (A320), FAA TCDS (737 and CFM LEAP-1B), Airbus, Boeing, and CFM International Commercial Materials
