The Alaska Airlines jet whose door blew off in mid-air was apparently missing bolts that should have been installed by Boeing employees when it rolled off of the aircraft manufacturer’s assembly line, according to a report.
An investigation into the incident revealed that Boeing employees may have failed to put back the bolts that would have sealed the plug door that was ripped off the 737 Max 9 aircraft as it flew 16,000 feet over Oregon in a Jan. 5 flight to California, according to The Wall Street Journal.
The fuselage of the 737 Max 9 was delivered by Wichita, Kan.-based supplier SpiritAeroSystems, which had the plug door constructed in a factory in Malaysia.
According to several reports, Boeing employees opened or removed the plug door after the fuselage was delivered to the company’s Seattle-area factory for final assembly.
Investigators believe that the absence of markings on the plug door suggests that Boeing personnel did not put the bolts back in as required, The Journal reported.