The incident with an Alaska Airlines aircraft has indirectly led to increased scrutiny on the 737 Max planes. If the additional inspections reveal more issues, it could lead to operational disruptions or negative publicity for Alaska Airlines, potentially affecting the stock price negatively in the short term.

As the supplier of the Max 9 door plugs, Spirit Aerosystems will be directly affected by Boeing's decision to implement additional quality inspections. This could lead to increased costs and potential delays in production for Spirit Aerosystems, which might have a negative impact on the company's stock price in the short term.

The additional inspections are likely to increase production costs and could potentially delay deliveries, which might negatively affect Boeing's short-term financial performance. However, the move is also likely to be seen as a positive step towards ensuring the safety and reliability of the 737 Max, which could help rebuild trust and potentially support the stock price.