What can a pilot do while on vacation?

A pilot on vacation is only permitted to pick up Voluntary Flight Notifications (VFN). This option is correct because it aligns with standard practices regarding pilot availability and work obligations. During vacation time, pilots are generally not required to work or take on additional responsibilities, which includes flying scheduled trips or completing assignments. Therefore, engaging in tasks beyond the scope of an informal notification, such as picking up VFN, ensures that they remain within the guidelines of their vacation status while still having the option to participate in voluntary flight opportunities.

The other options involve activities that would typically require an active duty status. For instance, assigning trips to other pilots or completing open assignments implies a responsibility that contradicts the nature of being on vacation. Similarly, flying scheduled trips would not be allowed since a pilot is considered off-duty and therefore unavailable for such operations.