Boeing works to correct 737 flight guidance software flaw

Boeing is working to correct a flaw in the 737’s automated flight guidance software
The issue happens following a missed approach when a pilot alters the programmed flight path
Southwest Airlines and United Airlines have requested Boeing pause deliveries of 737s with the flawed software
Boeing notified the FAA of the issue as part of its safety review process
Work is taking place under the FAA’s oversight to complete the software update

The US Federal Aviation Administration has proposed a new airworthiness directive targeting 95 US-registered Boeing 737 MAX aircraft due to a production quality control issue affecting critical flight control systems. The FAA’s proposed directive focuses on improperly installed bearings within the elevator buss assembly. This assembly is a mechanical system linking the cockpit control columns to the aircraft’s elevators, which directly manipulate the airplane’s pitch.

According to reports from the FAA Notice, some bearings were fitted without the mandatory sealant. This oversight could result in premature corrosion, cracking in the housing, and a subsequent failure of the assembly crank arms. If left uncorrected, the flaw poses a risk to overall pitch control, compromising safe flight and landing capabilities. The mandate does not ground the fleet but targets a specifically defined production window identified by Boeing. Models affected include specific 737 MAX 8, MAX 9, and high-density 737-8200 variants. Approximately 95 aircraft currently registered in the United States are affected.

Inspection time is estimated at 23 work-hours per aircraft. Base inspection cost is roughly $1,955 per aircraft, equating to roughly $185,725 for the entire US fleet. Potential repair costs range from $1,105 to $1,809 per bearing, escalating up to $98,500 per aircraft for a complete elevator buss assembly overhaul. The proposal remains open for public and stakeholder comments through November 2026 before transitioning into a finalised, legally binding rule.

The navigation issue, which Boeing informed operators of in August, comes as the company prepares to begin deliveries of the recently certified 737-7 and secure the long-delayed FAA approval for the stretched 737-10, the final version of the MAX family. Although Boeing states the software issue does not present a safety concern, it remains unclear if the problem will impact the timing of either milestone.

According to The Wall Street Journal, which first reported the problem, both Southwest Airlines and United Airlines have requested that Boeing pause deliveries of 737s with the flawed software but would take deliveries of aircraft with the earlier version of the software. Boeing stated it informed all 737 operators about a software issue where pilots may not have access to automated flight guidance during a specific landing scenario. The company shared information with operators that reinforced existing pilot procedures for safely handling such cases. Boeing engineers are working on a software update to permanently address the issue. The software problem happens following a missed approach, when a pilot alters the programmed flight path. At that point, according to Boeing, the flight management computer software issue may result in the flight guidance system incorrectly transitioning from VNAV mode to a simpler, more rudimentary level of automation for pitch control, like level-change or vertical speed.

Boeing states pilots are trained to safely land an airplane without automated vertical navigation. The company notified the FAA of the issue as part of its safety review process. Work is taking place under the FAA’s oversight to complete the software update. Boeing also states it is working directly with airlines to formalise a procedure that will allow pilots to re-enable automated VNAV should the situation happen.