What should a pilot monitor if RAIM is lost while in-flight?

Monitoring backup navigation aids, such as VOR, is crucial if RAIM (Receiver Autonomous Integrity Monitoring) is lost while in-flight. RAIM is a function of GPS systems that ensures the integrity of the GPS signals being used. If RAIM is lost, it may indicate that the reliability of the GPS signals has diminished, which could lead to inaccurate position information.

In such situations, it's essential for pilots to switch to an alternate navigation system to maintain situational awareness and ensure safe navigation. Backup navigation aids like VOR provide reliable and proven references that don't rely on satellite signals and help maintain a safe course.

Other choices may not provide the direct necessary solution in a RAIM loss scenario. While other GPS indicators or flight instruments might provide information about the state of the navigation system, they would not necessarily allow for a successful navigation alternative in the event of GPS signal loss. Aircraft maintenance reports have no relevance in real-time navigation decisions during a flight. Hence, the most effective course of action when encountering a loss of RAIM is to utilize backup navigation aids such as VOR.