Alaska Airlines flight was scheduled for security check the day sign exploded

A day before the door jam on an Alaska Airlines flight exploded on Jan. 5, the airline's engineers and technicians were so concerned about growing evidence of a problem that they wanted the plane be taken out of service the following evening and undergo maintenance. , interviews and documents show this.

But the airline opted to keep the plane, a Boeing 737 Max 9, in service Jan. 5 with some restrictions, carrying passengers until it completed three flights that were scheduled to end that night in Portland , Oregon, the site of one of the airline's maintenance facilities.

Before the plane could complete this planned flight sequence and pass maintenance check, the door plug exploded at 16,000 feet, minutes after boarding the second. Today's flight from Portland to Ontario International Airport in California.

The plane landed safely and no one was injured, but the incident focused new attention on Boeing's manufacturing processes and the safety procedures followed by airlines.

The aircraft's maintenance check scheduling has not been previously reported. This demonstrates that the airline chose to keep the plane in service while it headed to maintenance facilities rather than transport it to Portland without passengers.

Alaska Airlines confirmed the sequence of events. But the airline said the warnings it had on board the plane did not meet its standards to immediately take it out of service.

Donald Wright, vice president of maintenance and engineering for Alaska Airlines, said the warning signals – a light indicating problems with the plane's pressurization system – came on twice at over the previous 10 days instead of the three times the airline considers the trigger. more aggressive action.

Alaska Airlines has repeatedly asserted that there is no evidence that the warning lights, which could also be caused by electronic or other problems, were related to the impending spark plug blowout.

“From my perspective as a security leader, looking at all the data, all the leading indicators, nothing would have caused me to make a different decision,” said Max Tidwell, vice president of security and of Alaska Airlines Security. a meeting.

Airline engineers had requested that the plane undergo a rigorous maintenance check on January 5 to determine why the lights were flashing, based on their use of a “predictive tool” rather than the number of times when the lights went out. the airline said.

While keeping the plane in service, the airline imposed restrictions on it following recommendations from engineers. This prevented the plane from making long-haul flights over water, such as to Hawaii, or to remote mainland areas if an emergency landing was needed.

Extensive evidence of a potential problem with the plane had been accumulating for days, if not weeks, according to interviews with the airline and records from the blowout investigation. In addition to the flashing lights, investigators say the door stopper had gradually slid upward, a potentially crucial link in the accumulated body of evidence. The airline said its visual inspection in the days before the explosion revealed no movement of the door stopper.

A door stopper is a panel that goes where an emergency exit would be on an airplane with the ability to increase the number of passenger seats.

A preliminary report released last month by the National Transportation Safety Board indicated that four bolts intended to hold the door plug in place were missing before the panel came down from the plane. It described a series of events at Boeing's Renton, Washington, factory that could have led to the plane being delivered without those bolts in place.

Mark Lindquist, a lawyer representing passengers on the Jan. 5 flight, said the series of incidents involving the Alaska Airlines plane was alarming, adding that the carrier and Boeing, the maker of the 737 Max 9, would struggle to explain the events in court.

“When jurors find out that engineers advised them to ground the plane and instead put it into commercial rotation, they will be more than perplexed — they will be angry,” Mr. Lindquist said.

In his court filing, Mr. Lindquist said passengers on a previous flight heard a “hissing sound” coming from the door jam area. The documents say passengers reported the noise to the flight attendant, who then reported it to the pilots. When asked about the report, Alaska Airlines said it found no record of a whistling report coming from the plane.

Nearly a week before the explosion, the 737 was taken out of service on December 31 due to a problem with the front passenger entry and exit door. Records show the plane returned to service on January 2. However, on January 3, a pressurization warning light went off during at least one of the plane's flights. Alaska Airlines officials said the plane was inspected by engineers and the carrier determined it was safe enough for the plane to continue flying.

The next day, the same light went off again.

An Alaska Airlines spokeswoman said that's when engineers and technicians scheduled a further inspection of the plane for the night of Jan. 5 in Portland. But the airline chose to fly the plane with passengers as it crossed the country that day.

The revelations about the warning signs of a potential problem raised the question of whether routine inspections should have been able to combine various indications of a problem and avoid the incident.

Jennifer Homendy, chairwoman of the National Transportation Safety Board, told reporters last week that on the 154 flights the plane has made since it entered service in the fall, small upward movements of the door plug have left visible marks and had perhaps created a space between the panel and the fuselage.

Alaska Airlines officials said they did not notice any unusual gaps between the door plug and the plane's fuselage during inspections in the days before the door plug was removed.

Additional evidence includes pressurization system warning lights on previous flights and unconfirmed reports of a whistling sound.

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