Via Yahoo Finance

Boeing did not tell its largest 737 Max customer that a standard safety feature designed to warn pilots about malfunctioning sensors had been deactivated on the jets, The Wall Street Journal reports.

Southwest Airlines was unaware that the standard safety alert was turned off. The alert informed pilots if a sensor, known as an “angle-of-attack vane,” was transmitting faulty data about the pitch of the plane’s nose.

Boeing had installed a new anti-stall system on the 737 Max and made the safety alert — which was included in previous versions of the 737 — optional. The alert was operational only if the carrier bought additional safety features.

Federal Aviation Administration safety inspectors and supervisors were also unaware of the change, according to government and industry officials that spoke to the Journal.

Southwest did not know about the change for more than a year after the new 737 Max jets had gone into service. After the fatal crash of a Lion Air flight in Indonesia, Southwest asked Boeing to reactive the safety alert on the jets in its fleet.

The FAA even considered grounding Southwest’s Max fleet while they weighed whether or not the airline’s pilots needed additional training about the safety alert.

Boeing, in a statement to CNBC, said the “angle-of-attack”  disagree alert would be included as a standard Max feature.

“As we return to service, all customers will have the AOA disagree alert as standard and have the option to include the AOA indicator at no cost,” a spokesperson said. “This change will be made to all MAX aircraft – production and retrofit.”

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Southwest could not be immediately reached for comment.

Boeing’s 737 Max was grounded by the FAA in March in the wake of fatal crashes in Indonesia and Ethiopia that killed 346 people.

Several major airlines have extended Max cancellations through the summer. American has canceled Max flights through Aug. 19, totaling 115 flights per day, while Southwest has canceled through Aug. 5 and United through June 5.

Read the full report in The Wall Street Journal

— CNBC’s Spencer Kimball contributed to this report