A major factor behind Boeing’s delivery delays stems from two fatal crashes involving the MAX 8 model in late 2018 and early 2019. "On October 29, 2018, a Boeing 737 MAX 8 operating as Lion Air JT610 crashed into the Java Sea roughly 13 minutes after takeoff, killing all 189 people on board. Less than five months later, another Boeing 737 MAX 8 went down shortly after takeoff. The second aircraft, operating as Ethiopian Airlines ET302, was carrying 157 people onboard and went down in a chain of events concerningly similar to the JT610 crash. Together, 346 passengers lost their lives."

Following these incidents and subsequent investigations into flight control systems and manufacturing processes at both Boeing and its supplier Spirit Aerosystems—which assembles fuselages—the U.S. Federal Aviation Administration (FAA) grounded all global fleets of the model between March 2019 and November https://www.faa.gov/newsroom/faa-statement-continued-airworthiness-boeing-737-max.

During this period without deliveries or production at full capacity—and amid order cancellations during COVID-19—Boeing built up an inventory of undelivered planes known as “white-tails.” Some were eventually sold to new customers such as United Airlines and Alaska Airlines.

After being cleared by regulators starting in late https://www.faa.gov/newsroom/faa-statement-continued-airworthiness-boeing-737-max2020 , Boeing focused on delivering existing inventory before increasing output rates again. However production targets remained lower than pre-grounding levels due to ongoing quality concerns.

In January https://www.reuters.com/business/aerospace-defense/boeing-ceo-says-faa-production-cap-will-last-until-mid-year-wsj-2024-04-232024 , another incident involving an Alaska Airlines-operated MAX led to renewed scrutiny when a door plug detached mid-flight due to missing bolts—a failure traced back to quality lapses during assembly at Spirit Aerosystems. "The investigation exposed critical flaws in Boeing's and Spirit Aerosystems' (the contractor that assembles https://www.reuters.com/business/aerospace-defense/boeing-ceo-says-faa-production-cap-will-last-until-mid-year-wsj-2024-04-23/737 fuselages) quality control processes." As a result of this event and subsequent findings by regulators about broader manufacturing issues at both companies’ facilities , FAA imposed a cap limiting monthly output of new jets at thirty-eight per month . As of May https://simpleflying.com/boeing-may-deliveries-june-update/, Boeing had returned to this rate but requires further regulatory approval for any increase.

The lagging sales performance also reflects competitive dynamics: while both manufacturers see limited demand for their smallest models (A319neo vs. MAX7), Airbus’s A321neo dominates large narrowbody sales—a segment where Boeing’s offerings have struggled until certification of its largest variant (MAX10). "What's driving the A320neo program's success is the A321neo. With over https://simpleflying.com/airbus-a321-best-selling-aircraft-all-time/7 ,000 orders , it is the single best-selling aircraft variant of all time , and Boeing has lacked a real answer."

Looking ahead , certification efforts continue for outstanding variants like Max7 & Max10 alongside plans for higher output rates pending FAA approval . Despite setbacks & missed targets relative competitors like Airbus , industry observers expect thousands more Max jets will eventually enter service globally .