The Federal Aviation Administration on Thursday instructed airlines to inspect a pair of cabin air pressure switches on all Boeing 737 planes, citing safety concerns.
If the switches fail, oxygen levels could fall dangerously low inside a plane without warning. That could incapacitate flight crews, making them lose control of the plane.
“Addressing these failures requires immediate action,” the agency said in a directive.
Airlines have not reported any failures that led to a dangerous drop in oxygen levels during flight. But in September, an unnamed airplane operator said the switches on three planes — all different 737 models — had failed a test. Boeing decided late last year that those failures were not a security issue, but the company and the F.A.A. later concluded that they represented a threat after further investigation and analysis.
The F.A.A.’s directive applies to all 737 models, including the troubled 737 Max, which was banned globally in March 2019 after two fatal crashes. That ban began to be lifted late last year and the Max has been used on thousands of flights since.
The order, known as an airworthiness directive, makes mandatory a recommendation that Boeing issued to its customers last month, the company said in a statement. “Safety is our highest priority, and we fully support the F.A.A.’s direction,” Boeing said.
The order applies to about 2,500 planes in the United States and over 9,300 more worldwide. The switches must be inspected within 2,000 flight hours of the last time they were tested or within 90 days of the effective date of the order.