Boeing 737 MAX

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. …

In mid-2011, one design objective was matching fuel burn of the 737 MAX to that of the Airbus A320neo's 15% fuel-burn advantage. The initial 737 MAX reduction was 10–12%; it was later enhanced to 14.5%. The fan was widened from 61 inches (150 cm) to 69.4 in (176 cm) by raising the nose gear and placing the engine higher on the wing and further forward. The split tip winglet added 1–1.5% fuel burn reduction and a re-lofted tail cone another 1%. Electronically controlling the bleed air system improved efficiency. The new engine nacelle included chevrons, similar to those of the Boeing 787, which also helped to reduce engine noise.

The 737 MAX uses a split-tip winglet, designed to reduce vortex drag, which improves fuel efficiency by maximizing lift, while staying in the same ICAO aerodrome reference code letter C gates as current Boeing 737s. It resembles a three-way hybrid of a blended winglet, wingtip fence, and raked wingtip. A split-tip wingtip was first proposed for the McDonnell Douglas MD-12, a 1990s twin-deck aircraft concept. A MAX 8 with 162 passengers on a 3,000-nautical-mile (5,600 km; 3,500 mi) flight is projected to have a 1.8% lower fuel burn than a blended winglet-equipped aircraft (like many 737NG aircraft) and 1% lower over 500 nmi (930 km; 580 mi) at Mach 0.79. The new winglet has a total height of 9 feet 6 inches (2.90 m).

Other improvements include a re-contoured tail cone, revised auxiliary power unit inlet and exhaust, aft body vortex generator removal, and other small aerodynamic improvements.

In order to maintain sufficient engine ground clearance, the 737 MAX uses new engine mounts and pylons. This modified mounting arrangement moves the CFM LEAP engines higher and further forward as compared to the CFM56 engines used on the 737 Classic and 737 NG. The resulting change to the aerodynamic characteristics of the aircraft meant that the handling, feel, and stall recovery of the 737 MAX would have been different from previous models of the 737. Boeing wanted to ensure that pilots could fly the 737 MAX with their existing B737 type rating and minimal conversion training. …

After one year of service, 130 MAXs had been delivered to 28 customers, logging over 41,000 flights in 118,000 hours and flying over 6.5 million passengers. Flydubai observed 15% more efficiency than the NG, more than the 14% promised, and dependability reached 99.4%. Long routes include 24 over 2,500 nautical miles (4,630 km; 2,877 mi), including a daily Aerolíneas Argentinas service from Buenos Aires to Punta Cana over 3,252 nmi (6,023 km; 3,742 mi).

In 2019, Moody's had estimated Boeing's operating margin to be US$12–15 million for each 737 MAX 8 at its list price of $121.6 million (~$147 million in 2024), although the list price is usually discounted 50–55% in practice. This high margin was made possible by the efficiencies of production volume and the amortization of development costs and capital investment over the decades of the program run. However, costs have since risen significantly and the margin reduced following the two crashes, the FAA grounding, and the severe disruption to production. Boeing estimated it would cost an additional $6.3 billion to produce the remaining 737 MAX program, $4 billion for "future abnormal costs" as production restarted, plus an estimated $8.3 billion for concessions and compensation to customers. The rising costs also led Moody's to downgrade Boeing's credit rating.

The 737 MAX 7, MAX 8 and MAX 9 succeed the 737-700, -800, and -900ER, respectively—the most widely used variants of the previous 737 Next Generation series. Since 2020, their official FAA type certificate and marketing designations have been 737-7, 737-8, and 737-9. The MAX 8 entered service in May 2017, followed by the MAX 9 in March 2018, and the MAX 200, a high-density variant of the MAX 8, in June 2021. Deliveries of the MAX 7 and MAX 10 have not yet begun, following years of certification delays.

The MAX 8 is the most widely ordered variant. In 2018, Boeing projected that 60–65% of demand would be for the midsized MAX 8, 20–25% for the larger MAX 9 and MAX 10, and 10% for the smaller MAX 7.

At the July 2016 Farnborough Air Show, Boeing announced that the MAX 7, originally based on the 737-700, will accommodate two more seat rows than the 737-700 for 138 seats. Compared to the 737-700, the MAX 7 has a pair of over-wing exit doors rather than the single-door, a 46-inch (120 cm) longer aft fuselage and a 30-inch (76 cm) longer forward fuselage, structural re-gauging and strengthening, and systems and interior modifications to accommodate the longer length. The MAX 7 uses the same wing and landing gear as the MAX 8. It is expected to fly 1,000 nautical miles (1,900 km; 1,200 mi) farther than the -700 with 18% lower fuel costs per seat. Boeing predicts that the MAX 7 will carry 12 more passengers 400 nautical miles (740 km; 460 mi) farther than A319neo with seven percent lower operating costs per seat.

Production on the first 65-foot-long (20 m) wing spar for the 737 MAX 7 began in October 2017. Assembly of the first flight-test aircraft began on November 22, 2017, and was rolled out of the factory on February 5, 2018. The MAX 7 took off for its first flight on March 16, 2018, from the factory in Renton, Washington, and flew for three hours over Washington state. It reached 250 knots (460 km/h; 290 mph) and 25,000 feet (7,600 m), performed a low approach, systems checks and an inflight engine restart, and landed at Boeing's flight test center in Moses Lake, Washington.

Entry into service with launch operator Southwest Airlines was originally expected in January 2019; however, it has been repeatedly delayed. Southwest had ordered a total of 234 MAX 7s. WestJet also ordered 22 MAX 7s, but later converted those into MAX 8s amid the delays. …

As of October 2023, the five largest operators of the Boeing 737 MAX were Southwest Airlines (207), United Airlines (145), Ryanair Holdings (126), Alaska Airlines (62), and American Airlines (54).

American Airlines was the first disclosed customer. By November 17, 2011, there were 700 commitments from nine customers, including Lion Air and SMBC Aviation Capital. By December 2011, the 737 MAX had 948 commitments and firm orders from thirteen customers. On September 8, 2014, Ryanair agreed to 100 firm orders with 100 options. In January 2017, aircraft leasing company GECAS ordered 75. By January 2019 the 737 MAX had 5,011 firm orders from 78 identified customers, with the top three being Southwest Airlines with 280, flydubai with 251, and Lion Air with 251. The first 737 MAX 8 was delivered to Malindo Air on May 16, 2017.

Following the groundings in March 2019, Boeing suspended all deliveries of 737 MAX aircraft, reduced production from 52 to 42 aircraft per month, and on December 16, 2019, announced that production would be suspended from January 2020 to conserve cash. At the time of the grounding, the 737 MAX had 4,636 unfilled orders valued at an estimated $600 billion. Boeing produced over 450 MAX aircraft awaiting delivery, about half of which are expected to be delivered in 2021, and the majority of the remainder in 2022. By November 30, 2020, at the time of the ungrounding, the unfilled orders stood at 4,039 aircraft. In November 2021, during the Dubai Airshow, Boeing received 72 firm orders from a new 737 MAX customer, India based Akasa Air, to be fulfilled over a 4-year period with first delivery in June 2022. In late January 2022 Boeing was working to clear the remaining inventory of 335 MAX aircraft and estimated most of them would be delivered by the end of 2023. In December 2022, the 1000th 737 MAX was delivered. In July 2023, Boeing first revealed the 737 MAX sub-type orders as follows: 2,751 MAX 8 (63%), 810 MAX 10 (19%), 344 MAX 200 (8%), 297 MAX 7 (7%), and 137 MAX 9 (3%). As of September 2026, the 737 MAX has 4,867 unfilled orders and 2,483 deliveries. 737 MAX sub-type orders are as follows: 276 MAX 7, 2,967 MAX 8 (incl. 207 MAX 200), 180 MAX 9 and 1,444 MAX 10.