FAA Orders Fix for 737 Max Cabin Overheating Risk

The Federal Aviation Administration has issued an immediately effective airworthiness directive to address a safety concern involving the environmental control system on Boeing 737 Max aircraft that could cause cabins and flight decks to become dangerously hot.

The directive, issued on February 24, follows two incidents in which excessive cabin and cockpit temperatures could not be controlled by flight crews using existing procedures. According to the FAA, the problem has been traced to a tripped circuit breaker in the standby power control unit, which supplies power to air conditioning and cabin pressurization systems.

Investigators determined that the tripped circuit can generate an unintended electrical ground signal, prompting actuators to close both ram air deflector doors. These doors regulate airflow to the aircraft’s air conditioning heat exchangers. When closed, the system may deliver excessively hot air into the cabin and flight deck, potentially leading to uncontrollable high temperatures.

The FAA warned that, if left unaddressed, the condition could result in injury or incapacitation of flight crew and passengers. The order applies to all US-registered 737 Max aircraft currently in service, including the 737-8, 737-8-200, and 737-9 variants.

Operators have 30 days to revise aircraft flight manuals to incorporate updated non-normal procedures detailing how pilots should respond to tripped breakers and elevated cabin temperatures. The directive takes effect immediately, bypassing the FAA’s standard notice-and-comment rulemaking process. However, the agency will accept public comments through April 10, citing the urgency of mitigating risks to the flying public.

Boeing said it supports the FAA’s action, noting that guidance was previously provided to operators in January 2026. The manufacturer identified the root cause as a ground wire fault within the air conditioning system and is developing a permanent engineering solution to eliminate the electrical vulnerability.

Boeing stated that the fix will be incorporated into the 737-8 and 737-9 fleets and will be available for the 737-7 and 737-10 ahead of their certification. The company added that it does not expect the issue to impact the certification timeline for the long-delayed 737-7 and 737-10 models. Earlier-generation 737 aircraft are not affected by the issue.

Sources: AirGuide Business airguide.info, bing.com, flightglobal.com