Shares of Boeing have experienced a sharp decline of nearly 10% this week following an incident involving a door plug on one of its 737 Max 9 aircraft during an Alaska Airlines flight. The incident occurred on Friday night, leading to the Federal Aviation Administration (FAA) grounding the affected aircraft. As a result, the stock price of Spirit Aerosystems, the manufacturer of the door plug, has also fallen by over 11% since Monday's trading.

The National Transportation Safety Board (NTSB) has launched an investigation into the incident. According to the NTSB, the Alaska Airlines flight, with 171 passengers on board, was en route from Portland International Airport when the door plug detached from the aircraft at an altitude of 16,000 feet. Fortunately, no serious injuries were reported among the passengers or crew.

Bank of America, in a note to investors, maintained its recommendation to buy Boeing shares but cautioned about potential negative effects on public perception of the company. The incident has raised concerns about the fragile confidence surrounding the 737 Max franchise, prompting the bank to emphasize the need for Boeing to navigate this reputational challenge with caution.

On Monday, United Airlines announced that loose bolts had been discovered on its 737 Max 9 fleet during inspections conducted in response to the incident. This development indicates that the investigation by the NTSB could expand to include additional aircraft as more information becomes available.

Boeing expressed its support for the FAA's decision to ground the 737 Max 9 aircraft and to conduct a thorough investigation. The company highlighted its commitment to safety and acknowledged the impact the incident has had on its customers and their passengers.

This incident comes five years after the global grounding of Boeing 737 Max aircraft following two fatal crashes in Indonesia and Ethiopia that claimed the lives of 346 people. In 2021, the aircraft were allowed to resume operations after a two-year ban. In addition to the safety concerns, Boeing has faced challenges related to a decline in demand due to the COVID-19 pandemic and a recent supply chain slowdown related to issues identified in the 737 Max.

Speaking during an earnings call in October, Boeing CEO Dave Calhoun acknowledged the difficulties the company has faced in recent months but expressed optimism about the recovery process. He emphasized the company's efforts to enhance quality processes and foster a culture of transparency.

As the investigation into the door plug incident continues, the spotlight remains on Boeing and its ability to address safety concerns and restore trust among customers and the public. The outcome of the investigation and any subsequent actions taken by regulatory agencies will likely have a significant impact on the company's reputation and future prospects.