The US Federal Aviation Administration grounded the MAX 9 for several weeks in January and has capped Boeing's production of the MAX while it audits the planemaker's manufacturing process. The door panel that flew off the jet appeared to be missing four key bolts, according to a preliminary report from US the US National Safety Transportation Board in early February. According to the report, the door plug in question was removed to repair rivet damage, but the NTSB has not found evidence the bolts were reinstalled. The panel is a plug in place on some 737 MAX 9s instead of an additional emergency exit. Boeing shares were down 0.3% on Wednesday. Reuters