https://www.bbc.com/news/articles/cx2gy78gpnqo
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It says in December 2018, the US Federal Aviation Administration issued a Special Airworthiness Information Bulletin (SAIB) highlighting that some Boeing 737 fuel control switches were installed with the locking feature disengaged.
While the issue was noted, it wasn't deemed an unsafe condition requiring an Airworthiness Directive (AD) - a legally enforceable regulation to correct unsafe conditions in a product.
The same switch design is used in Boeing 787-8 aircraft, including Air India's VT-ANB which crashed. As the SAIB was advisory, Air India did not perform the recommended inspections