The FAA is investigating whether a glitch stemming from a software update to the flight management computer (FMC) on Boeing 737 Max aircraft poses a safety concern for pilots, as the manufacturer works to resolve the potential issue.
The glitch, which according to Aviation Week could incorrectly disengage the 737 Max’s vertical navigation system (VNAV) and transition to simpler automated guidance during certain landing scenarios, was first reported Saturday by the Wall Street Journal. Per the report, Boeing was first made aware of it in 2024 and in September convened a formal safety review board, which has shared its findings with the FAA. The glitch had not been disclosed publicly.
Citing company documents, the Journal reported that Boeing has informed airlines the glitch does not pose a safety concern. But several 737 Max 7 and Max 10 customers have said they will not take delivery of aircraft with the software update.
According to the Journal, jets flying for Alaska Airlines, American Airlines, Southwest Airlines, and United Airlines do not use the new software. However, CBS News reported that the Max 7 and Max 10 each use versions of it.
“The FAA is aware of a potential issue in a software update for the flight computers on certain Boeing 737 Max airplanes and is working closely with Boeing and the airlines,” the agency told FLYING. “The FAA will convene a Corrective Action Review Board (CARB) and will take immediate action if it identifies a safety concern.”
The CARB will comprise FAA safety experts and is intended to determine whether the issue is a safety concern and, if so, how to address it. The agency said it will review Boeing’s proposed solution to the glitch.
“We shared information with operators that reinforced existing pilot procedures for safely handling such cases,” Boeing said in a statement to the Journal. “Our engineers are working on a software update to permanently address the issue.”
According to the report, Boeing is developing a procedure that would allow pilots to re-enable VNAV if needed. The company in August told 737 Max operators that more guidance will be forthcoming in November and a permanent fix for the glitch could arrive by 2028, adding that it is working to accelerate those timelines.
Glitch in the System
The Journal reported that the 737 Max software glitch emerged following a cockpit software update developed by GE Aerospace, which it said is working with Boeing and the FAA to study it.
A Max operator informed Boeing of the issue in November 2024, but the company in early 2025 determined it did not require an internal safety review, according to CBS News. Citing an unnamed source, CBS said Boeing launched a formal review in September after obtaining “additional information from operators” earlier this year. Its findings have been shared with the FAA and will be reviewed by the CARB.
According to CBS, the software glitch could activate under rare circumstances, typically near airports at low-altitude where pilot workload is already high, and require added manual control.
According to Aviation Week, the issue manifests when a pilot flying a precision approach with autopilot engaged initiates a missed approach, the instrument version of a go-around. During a missed approach, the aircraft is supposed to climb. The malfunction causes the automated flight guidance system to incorrectly drop from VNAV to basic pitch control—which requires the pilots to handle pitch and navigation adjustments—if the preprogrammed flight plan is changed.
VNAV follows the vertical profile computed by the FMC using the flight plan’s altitude and speed limits. Neither level change nor vertical speed modes, which respectively hold a target airspeed and rate of climb or descent, follows the FMC’s vertical profile, which would require pilots to manage constraints manually should VNAV be disengaged.
A Boeing spokesperson told CBS that autopilot will continue to function even if VNAV disengages and that pilots are trained to land safely without it.
“This is not considered a safety issue, we have standard operating procedures and training to mitigate this type of event,” Canada’s WestJet told the Journal.
CBS reported that the glitch appears in Versions 14 and 14.1 of the 737 Max FMC’s operating system. The Max 7 was certified in August with Version 14, and the Max 10 used Version 14.1 during its certification testing, per the report.
“United does not currently have any 737s operating with this new FMC software, and we are not taking deliveries of new aircraft with the new FMC software,” the carrier told digital aviation news outlet Simple Flying.
Similarly, Southwest told CNBC that “none of our fleet is equipped with Version U.14, including new deliveries of Max 8 airplanes.”
Citing unnamed industry officials, the Journal reported that both carriers do not want new 737 MAX planes equipped with the software update and have requested an earlier version of it.
Boeing told the Journal it is working on an accurate count of the number of jets flying with the flawed software. It is unclear how many aircraft flown by non-U.S. operators or undelivered jets may use it. Per Cirium data, there are approximately 2,400 Max 8 and 9 models in operation globally.
Ripple Effect
Though the potential safety issue stemming from the glitch does not appear to affect 737 Max aircraft currently operated by U.S. airlines, it may impact deliveries of the Max 7 and certification of the Max 10.
The FAA in August awarded Boeing an amended type certificate for the Max 7, clearing it for service once deliveries begin. The Max 10 is not yet certified, but Reuters last week reported that Alaska expects that to happen in September, with deliveries and commercial launch following in the spring.
However, Boeing told Airways Magazine that it had no further information on whether 737-7 deliveries could proceed with an earlier version of the software, as Southwest and United reportedly requested. Also unclear is whether the MAX 10 could be certified with an earlier version, or if the FAA’s CARB would need to conclude before that happens.
Delta Air Lines, United, American, and Alaska are among the airlines with orders for the 737-10, whose certification has been delayed for years. Alaska is the intended launch operator.
Southwest has placed over 300 orders for the 737-7 and is the launch customer for the type, comprising the bulk of its order book. The carrier aims to begin flying them next year and has already waited several years for delivery.
Should the FAA determine the glitch to be a safety concern, it could spell more trouble for the long-beleaguered 737 Max family.
The agency grounded hundreds of Max 8 aircraft in 2019 following two fatal accidents that killed a total of 346 people. The incidents occurred less than five months apart and were linked to the activation of the jets’ Maneuvering Characteristics Augmentation System (MCAS). Boeing removed a description of MCAS, which was found to have a design flaw, from the Max 8’s manual before it entered service.
MCAS was designed to automatically adjust the aircraft’s horizontal stabilizer to push down the nose and prevent pilots from flying at too steep an angle, but operators were given inadequate information about how to disable it. During the two fatal crashes, MCAS activated without pilot input due to false sensor data and repeatedly pushed down the jets’ noses. Crews were unable to identify the problem and recover in time.
The FAA ended the Max 8’s grounding, which was the longest ever for a U.S. airliner and resulted in hundreds of cancelled orders and billions of dollars in losses for Boeing, in November 2020. In early 2024, the agency briefly grounded Max 9 aircraft following the Alaska Airlines door plug blowout.
The groundings delayed FAA approval of newer versions of the Max. Boeing will hope to avoid a similar outcome should the agency deem the new software glitch to pose danger.