On Friday, January 5, 2024, Alaska Airlines Flight 1282 had a normal departure and climb-out from Portland en route to Ontario, California. There were 171 passengers on board, with six crewmembers.  As the 737 Max was ascending through 16,000 feet, traveling at approximately 440 mph, there was a rapid decompression caused by a complete fuselage panel breaking free from the left side of the passenger cabin, just behind the left wing.

The panel was apparently a plug that could be converted into a door at a later date if needed. The location does not have the normal structural ribbing of the fuselage but has a framed opening plugged by the panel and its window, as indicated in the photo below.

These 171 passengers and six crew members are very lucky. This panel could have launched into the tail section and struck a horizontal stabilizer with catastrophic consequences. The event could have also compromised the structural integrity of the remaining fuselage.

The aircraft, N704AL, is a very new airplane, entering into service in November 2023, shortly after the FAA issued its airworthiness certificate.

This event should not be minimized by calling it a mishap or incident. It was an accident but with very lucky results. An “accident” as defined by federal law under 49 U.S.C. §830.2 because it involved substantial damage to the exterior of the aircraft, which adversely affects the performance or flight characteristics of the aircraft.

That is the definition that the NTSB uses, and the FAA is taking this accident very seriously. As of Saturday morning, the FAA will issue an Emergency Airworthiness Directive that grounds all 737 Max 9 aircraft in the United States.

“The FAA is requiring immediate inspections of certain Boeing 737 MAX 9 planes before they can return to flight,” FAA Administrator Mike Whitaker said. “Safety will continue to drive our decision-making as we assist the NTSB’s investigation into Alaska Airlines Flight 1282.”

FAA Statement on Temporary Grounding of Certain Boeing 737 MAX 9 Aircraft | Federal Aviation Administration

The full text of the Emergency Airworthiness Directive is available at the end of this post.

Three Common Failure Modes Worth Consideration.

Aviation Law Group’s investigation of this event is in its preliminary stages, and we are evaluating three common failure modes that can be found in aviation accidents.

First, design defect. This involves a problem with the design of the 737 Max, which is insufficient. It would exist in all similar 737 Max aircraft of similar design. Aircraft history is important. The 737 Max program was launched in 2011, and production aircraft were first built in 2015. Since then, approximately 1400 737 Max aircraft have been built. However, we do not know how many of these have door frames designed into them that contain fill-in plug panels. While we are not aware of any similar failures (though the 737Max has a history of other significant problems), design defects cannot be ruled out. There is probably more to the story.  Since design defects may exist in all aircraft of similar design, the airline and the FAA may ground all similar aircraft until the problem is fixed in each aircraft.

The second is a manufacturing defect. This occurs when a part of a plane is not built according to the design plans.  This may arise during assembly or during selection and use of component parts that are different from what the design specifications call for. In either case, manufacturing defects are evaluated on a plane-by-plane basis, and design specification compliance should also be affirmed through paperwork and assembly records. We suspect that some manufacturing defect in assembly or in a component part use may have contributed to the failure. However, more facts are needed to evaluate this.

Third is negligent maintenance. This may arise after the aircraft is operating in the field and undergoes maintenance. It may arise during inspection, maintenance, re-assembly, or use of unapproved parts. However, a new aircraft usually does not undergo significant maintenance, calling for a complete airframe inspection during its first two months of operation. Thus, more facts are needed to evaluate any maintenance-related issues.

Pressurization on Modern Jetliners

Pressurized aircraft, like all modern commercial aircraft, including Boeing and Airbus, seek to maintain a comfortable environment for their passengers while traveling in extremely inhospitable flight conditions at jet cruising altitudes. For many reasons, commercial jet aircraft typically seek to fly between 30,000 and 41,000 feet in altitude where the atmospheric pressure and outside air temperature are too low to sustain human life.

The cabin is pressurized by forcing air into the passenger cabin at a greater rate than it is allowed to escape the cabin through what is called an outflow valve. This influx of pressurized air in relation to a lesser amount of air allowed to escape from the aircraft cabin causes the pressure to build to a point that is suitable for passenger comfort; in most cases, roughly the equivalent of 6,000 to 8,000 feet in altitude while the aircraft is traveling above 30,000 feet.

Ambient, or outside air, is bled off from the engine at different stages as the air passes through the jet engine before it reaches the combustion section of the jet engine. This bleeding air has been compressed by several stages of fan blades in the engine, thus increasing the density of air molecules and heating the air. This compressed bleed air is sent to the PACKS (pneumatic air conditioning kits) where the air is heated and cooled in a process that prepares it for entry into the passenger cabin.

The outflow valve is typically located toward the rear of the aircraft fuselage and regulates how much of the incoming bleed air from the PACKS is allowed to escape the passenger cabin. The outflow valve can be controlled manually but is typically controlled automatically by cabin pressure control computers on modern commercial jet aircraft. As the bleed air enters the cabin at a higher rate than is allowed to escape, cabin pressure increases. The outflow valve modulates to maintain a comfortable cabin pressure for passengers during the ascent, cruise, and descent segments of the flight.

Pressurization systems contain safety valves that will automatically open if cabin pressure exceeds certain pressurization differential thresholds to prevent overpressure of the passenger cabin.

Aviation Law Group attorneys have handled many aircraft depressurization cases. Emotional distress from these types of accidents can be significant, sometimes caused by the accident creating fear of impending doom. PTSD, even days or weeks later, could develop.  In addition, the rapid decompression of the air caused by the normally pressurized cabin decompressing when the fuselage is breached may cause internal physical injuries such as inner ear damage resulting in partial or complete loss of hearing or possibly lung trauma if the decompression is more explosive.

The full text of the Emergency Airworthiness Directive is available below.