Boeing believed a 737 Max warning light was standard. It wasn’t.

Work on a Boeing 737 Max 8 plane at the company's plant in Renton, Wash., March 20, 2019. Confusion inside Boeing about features related to a new software system underline the flawed design and rollout of the company’s troubled new jet. PHOTO | REUTH FREMSON | NEW YORK TIMES

When Boeing began delivering its 737 Max to customers in 2017, the company believed that a key cockpit warning light was a standard feature in all the new jets.
But months after the planes were flying, company engineers realised that the warning light worked only on planes whose customers had bought a different, optional indicator.

In essence, that meant a safety feature that Boeing thought was standard was actually a premium add-on.

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