The US Federal Aviation Administration has concluded that a software anomaly in the flight management computer (FMC) of the Boeing 737 is not a safety concern. A panel of FAA safety experts, the Corrective Action Review Board (CARB), reached that decision in Seattle on Friday 2 October3. According to Reuters, the FAA based it on the fact that "pilots retain full control of the aircraft and the indications to the flight crew are clear and unambiguous"3. The ruling removed a late obstacle to certification of the 737 MAX 10, which the FAA had delayed in late September until it completed its analysis of the software issue35.

What happens on the flight deck

The anomaly affects FMC software versions U14.0 and U14.1. The FAA bulletin describes two conditions: it occurs after a missed approach, when the crew navigates direct to a waypoint that is not part of any approach or approach transition for that airport. During the subsequent approach, the aircraft then transitions out of vertical navigation (VNAV) to a simpler level of automation for pitch control. If the crew want to use VNAV on that next approach, they have to carry out additional procedural steps1. Boeing's own guidance documents describe the trigger as a VNAV disconnect when the MCP altitude is raised for a missed approach after a go-around1.

According to Boeing's description of the problem, as reported by Aviation Week and cited by Airways, the system may revert to level change or vertical speed6. In level change the aircraft holds a target speed while the autothrottle sets climb or idle thrust; in vertical speed it holds a rate the pilot selects. Neither follows the vertical path the FMC builds from the procedure's altitude and speed constraints, so the crew have to manage those constraints themselves6. Boeing says the autopilot keeps working if VNAV drops out and that all pilots are trained to land without VNAV5. CBS notes the scenario would typically occur low and close to the airport, where pilots already have a high workload56.

What the FAA requires, and what it recommends

Nothing is mandatory. In Special Airworthiness Information Bulletin (SAIB) 2026-17, dated 3 October, the FAA says the issue is "not an unsafe condition that would warrant airworthiness directive (AD) action" and that its recommendations are not mandatory1. The bulletin covers the 737-600, -700, -800, -900 and -900ER and the MAX models 737-7, -8, -9 and -8200, where U14.0 or U14.1 is installed1. The bulletin has also been listed in EASA's online airworthiness directives database since 9 October2.

The FAA recommends that operators follow the guidance Boeing produced for the scenario: Fleet Team Digests for the MAX (revised) and the Next Generation, and a Flight Crew Operations Manual bulletin titled "VNAV Approach Disconnect Following Missed Approach", all dated 2 October1. Boeing has also said it is working with airlines on a procedure that lets pilots "re-enable automated vertical navigation should this situation occur"3. A permanent software fix was first planned for 2028; Boeing says it is trying to bring that forward5.

What it means for crews and trainees

For crews on aircraft running U14.0 or U14.1, the practical point is that the operator's version of the Boeing bulletin is the reference, not a press summary. Whether a given fleet is affected depends on the installed FMC software, not on the aircraft model alone: Alaska Airlines, American Airlines, Southwest Airlines and United Airlines all said none of their in-service MAX aircraft use the affected versions5. WestJet, which found the anomaly on an entry-into-service test flight in November 202437, does use U14.1. Its staff memo said: "WestJet has received no reports of this condition occurring during normal line operations"3.

The wider lesson is mode awareness. The flight mode annunciator, usually across the top of the primary flight display, shows which autothrottle, lateral and vertical modes are armed or active9. SKYbrary notes that pilots "should not just press a button to make a selection" but should then check the FMA to confirm the system is doing what they intended9. An unexpected change from VNAV to another pitch mode is exactly the kind of transition that scan is meant to catch.

The MAX 7 and MAX 10

While the older U13 software is available for the MAX 8 and 9, the MAX 7 and MAX 10 rely on the newer versions7. The FAA certified the MAX 7 on 3 August with U14, and the MAX 10 used U14.1 throughout its certification flight testing85. According to Aviation Week, the FAA will not require Boeing to update the software before certifying the MAX 104. As of 17 October, Simple Flying, citing The Air Current, reports that the FAA's Type Certification Board met on 16 October and that the type certificate could be signed as early as the following week7. United has said it is not taking new aircraft fitted with U14 or U14.17.

Frequently asked questions

Did the FAA ground any 737s or issue an airworthiness directive?

No. The FAA found the anomaly is not an unsafe condition and issued an information bulletin with non-mandatory recommendations1.

Which software versions are affected?

FMC software U14.0 and U14.1, on 737 Next Generation and 737 MAX aircraft that have those versions installed1.

Does the autopilot disconnect?

No. According to Boeing, the autopilot keeps working; VNAV reverts to a simpler pitch mode and the crew need extra steps to use VNAV on the next approach51.