To develop an internal audit plan that aligns with ISO 9001 standards, focusing on the most critical areas for compliance, you can follow these steps:

1. **Conduct a GAP Analysis**: Determine the extent to which your organization already complies with ISO 9001:2015. This will help identify areas that need attention.

2. **Establish a Project Plan**: Define activities, deadlines, and other relevant information needed to address the gaps identified in the GAP analysis.

3. **Plan the Audit Schedule**: Determine the frequency and timing of audits based on the importance of the processes and previous audit results.

4. **Define Audit Criteria and Scope**: Clearly outline what will be audited and against which criteria, ensuring all requirements of the standard are covered.

5. **Ensure Auditor Competence**: Make sure your internal auditors are trained and competent, and that they do not audit their own work to maintain objectivity.

6. **Conduct the Audit**: Follow a structured process to evaluate compliance with ISO 9001, focusing on complex processes and areas with a high probability of nonconformities.

7. **Report and Follow-up**: Document the audit results, communicate them to relevant management, and follow up on any issues or improvements identified.

8. **Management Review**: Conduct a management review to assess the effectiveness of the QMS and the audit process.

By following these steps, you can ensure that your internal audit plan is comprehensive and aligned with ISO 9001 standards.