The U.S. Federal Aviation Administration (FAA) has concluded that a software anomaly identified in the flight management system of certain Boeing 737 aircraft does not constitute an unsafe condition that would require the certification of the 737-10 to be halted. The decision removes one of the remaining potential obstacles facing the largest member of the 737 MAX family, whose certification is expected during October.

The FAA’s Corrective Action Review Board (CARB) reviewed the issue on October 2 and concluded that pilots retain full control of the aircraft if the anomaly occurs, while indications of the system’s mode change are sufficiently clear and unambiguous. The regulator therefore does not currently consider the problem a safety deficiency requiring an mandatory airworthiness directive. Reuters reported that the decision removed significant uncertainty surrounding the completion of the 737-10 certification process.

The issue can occur in a specific scenario during a missed approach, or go-around. If the crew modifies the previously programmed flight path, the VNAV vertical navigation system can disengage under certain circumstances. The aircraft then transitions to a simpler vertical guidance mode, such as Level Change or Vertical Speed, requiring additional crew input to ensure the aircraft continues to follow the intended vertical profile.

According to Aviation Week, the possibility of increased pilot workload during a missed approach was one of the reasons the issue attracted additional attention from regulators and airlines. A go-around is a standard manoeuvre for which crews are trained and which is considered during approach preparation, but it is also a phase of flight in which aircraft configuration, thrust, vertical path and navigation requirements can all change within a short period of time.

Following its assessment, the FAA issued Special Airworthiness Information Bulletin SAIB 2026-17 on October 3. According to available information, the document applies to Boeing aircraft equipped with Flight Management Computer software versions U14.0 and U14.1, including certain 737 Next Generation aircraft as well as the 737 MAX. The FAA did not mandate a software modification, instead recommending that operators follow Boeing’s operational guidance for recognising and managing the anomaly.

The U14 software is particularly important for the newest MAX variants. Version U14.1 is currently the only version compatible with the 737-7 and 737-10, while existing 737-8 and 737-9 aircraft can also operate with earlier software versions. Boeing and system supplier GE Aerospace are working on a permanent software update intended to eliminate the anomaly.

The issue was first reported in 2024. According to Reuters, Canadian carrier WestJet alerted Boeing to unusual system behaviour during validation flights. Boeing subsequently analysed the problem and concluded that a correction was necessary, but that the anomaly did not represent an immediate flight safety risk. The matter was revisited during 2026 following additional operator reports, after which it was referred to the FAA for an independent assessment.

Although the regulator accepted Boeing’s risk assessment, the question of whether airlines are willing to accept aircraft with the affected software remains separate from the question of airworthiness. United Airlines and Southwest Airlines are among the operators that have indicated they do not want to take delivery of new aircraft with the flawed software, while some other U.S. carriers have also avoided moving to the latest FMS versions. The Air Current reported that some U.S. operators have preferred to retain older, proven software versions following a series of issues reported with newer releases.

To keep deliveries of the existing 737-8 and 737-9 variants moving, Boeing has begun reverting some newly built aircraft to older FMS software versions that are not affected by the anomaly. Aviation Week reported that this approach was introduced specifically in response to customers that did not want to accept aircraft equipped with U14 before a permanent software solution became available.

The FAA’s decision is particularly significant for Boeing because the 737-10 is now in the final stage of its development and certification programme. The largest MAX variant completed its planned certification flight test programme at the end of July after 976 flights and more than 2,060 flight hours. Remaining work has largely centred on final documentation reviews, system safety assessments and other development checks required before certification can be granted. In mid-September, Boeing said certification was “very close”.

The 737-10 is intended to carry around 185 to 210 passengers in a typical two-class configuration, with a range of approximately 3,100 nautical miles. Boeing positions it as a direct competitor to the Airbus A321neo, with one of its main commercial advantages expected to be lower seat-mile costs compared with smaller MAX variants. The programme, however, is already several years behind its original schedule.

The FAA’s decision does not mean the software issue has been closed. Boeing and GE Aerospace still need to complete a permanent correction, while individual operators will decide whether they are prepared to accept new aircraft before the revised software becomes available. From a regulatory standpoint, however, one potential obstacle to the certification of the 737-10 has now been removed: the FAA has determined that the existing system behaviour does not cross the threshold of an unsafe condition because it is clearly recognisable to pilots and does not compromise aircraft controllability.