How is it verified that the main cabin door is closed?

The main cabin door's closure is verified using the DOORS page and eight witness marks because this method provides a standardized and comprehensive assessment of the door's status. The DOORS page displays detailed information about the door's configuration and any discrepancies. The presence of the eight witness marks serves as a physical and visual check, ensuring that the door is in the fully closed and secured position. This multi-faceted approach ensures that the procedure is not solely reliant on visual confirmations or indicators, which might be susceptible to error.

Verifying the door's closure through indicators or visual inspections can be less reliable, as these methods may not provide definitive evidence of the door's secure state. Confirmation from the pilot is important during operations, but it is not as effective as having a specific procedure that includes verification methods like the DOORS page and witness marks. Thus, the combination of these tools ensures safety and compliance with standard operating procedures.