What should a pilot do if the glide slope warning flag appears immediately after passing the final approach fix during an ILS approach?

When a glide slope warning flag appears after passing the final approach fix during an ILS approach, it indicates a malfunction or loss of the glide slope signal. Choosing to continue the approach and descend to the localizer minimum descent altitude (MDA) is a prudent course of action because the localizer can still provide lateral guidance for the approach.

This decision is based on the understanding that if the glide slope is lost but the localizer remains functional, the pilot can still execute the approach visually once reaching the MDA. At this point, the pilot should be prepared to transition to visual flight rules for landing and maintain a careful lookout for the runway environment. Safety is paramount, and following this procedure allows the pilot to maintain control and ensure a safe outcome despite the glide slope failure.

It's important to be aware of the approach plate's specified minimums and approach procedures for the specific runway as these guide the decision-making process during such an event.