Alaska Airlines flight was headed for maintenance the same day part of the plane blew off

Alaska Airlines flight 1282, on which a door plug blew off the side of the plane shortly after takeoff on January 5, was scheduled to be taken out of service for maintenance the night of the incident, the airline said Tuesday.

Although Alaska Airlines did not say why the plane was set to be taken out of service, the airline told the New York Times, which first reported the scheduled safety check, that the plane was set to be removed from service to investigate two separate warning lights that alerted the crew to a potential pressurization problem on the plane over the 10 days prior to the blowout.

Jennifer Homendy, chair of the National Transportation Safety Board, told CNN on January 8 that she was aware the plane had pressurization issues before the door plug blew out, and the safety regulator planned on probing Alaska Airlines about the incident. But the NTSB later clarified that it believed the pressurization warnings were unrelated to the side of the plane blowing out mid-air.

The NTSB said the warning started appearing just weeks after the plane was delivered, in early December, and most recently happened the day before the door plug blowout incident.

Max Tidwell, the vice president for safety and security for Alaska Airlines, told the New York Times that the airline did not believe the indicator lights posed a serious enough problem to take the plane out of service sooner without carrying passengers.

Such deferred maintenance is common and legal, and the plane had made 154 successful flights before the blowout.

In its preliminary investigation, the NTSB found that Boeing probably did not put required bolts in the door plug. The bolts are designed to prevent that part from blowing off the plane.

It’s not clear that an expedited maintenance schedule would have led Alaska Airlines to discover that problem. However, engineers were concerned enough about the warning lights that the airline prevented the plane from carrying passengers on long-haul routes over water in case of emergency, according to The New York Times.

“The U.S. aviation system is the safest in the world because it relies on layers: redundant systems, robust processes and procedures, and the willingness to stop and ensure things are right before every takeoff,” Alaska Airlines said in a statement. “We remain confident in our maintenance and safety actions leading up to the incident. We look forward to continuing our participation in a robust investigation led by the NTSB to ensure something like this never happens again.”

Alaska Airlines’ (ALK) stock fell marginally in after-hours trading. The airline has largely avoided heavy scrutiny in the incident as blame has largely been laid on Boeing following the preliminary results of the probe. Boeing has been subject to congressional hearings, production and delivery delays, multiple federal investigations — including a criminal probe — and a stock that has lost more than a quarter of its value this year, shaving more than $40 billion off the company’s market valuation.

Although the revelation that the plane was scheduled for service the same day as the blowout does not necessarily suggest any wrongdoing by Alaska Airlines, it does raise further concerns about policies and regulations surrounding maintenance of America’s fleet of aircraft.