When an unforeseen event causes a delay, especially one that affects the critical path, the project manager should review the project management plan to understand the full impact of the delay on the project's objectives. This review will help in assessing the situation and deciding on the next steps, which may include re-sequencing activities, performing schedule compression, or negotiating changes to the project's scope or deadlines.
References: = The PMBOKGuide emphasizes the importance of the project management plan as the primary document for understanding the project's objectives and how they are to be achieved. It also outlines the need for regular monitoring and controlling of the project's progress to manage any changes or delays effectively12. Additionally, the guide discusses various strategies for dealing with delays, including but not limited to, schedule compression techniques like crashing and fast tracking34.

When senior managers are unaware of a deliverable, it indicates a communication gap that needs to be addressed promptly. The project manager should meet with these stakeholders to review the project charter, which includes information on all key deliverables. This action aligns with the PMI's principles of stakeholder engagement and communication management, ensuring that all stakeholders have a clear understanding of the project's objectives and deliverables123. It is also consistent with the practices outlined in the Business Analysis Body of Knowledge (BABOK), which emphasizes the importance of stakeholder engagement and the need for business analysts to facilitate clear communication about project requirements and deliverables456. References: = Project Management Institute's resources on project communication and stakeholder engagement123, and the Business Analysis Body of Knowledge (BABOK)456.