The agency and the National Transportation Safety Board opened separate investigations of Boeing that are continuing. Calhoun said Boeing has responded to the Alaska accident by slowing production, encouraging employees to report safety concerns, stopping assembly lines for a day to let workers talk about safety, and appointing a retired Navy admiral to lead a quality review. Late last month, Boeing delivered an improvement plan ordered by the FAA. Calhoun defended the company's safety culture while acknowledging that it "is far from perfect." The drumbeat of bad news for Boeing has continued in the past week. The FAA said it was investigating how falsely documented titanium parts got into Boeing's supply chain, the company disclosed that fasteners were incorrectly installed on the fuselages of some jets, and federal officials examined "substantial" damage to a Southwest Airlines 737 Max after an unusual mid-flight control issue.