What might be indicated if a fuel pressure gauge shows rapidly fluctuating readings during flight?

A rapidly fluctuating fuel pressure gauge reading during flight is primarily indicative of fuel vaporization occurring in the system. When fuel vaporizes, it can create bubbles or vapor pockets in the fuel line, leading to inconsistent pressure readings as the pump tries to push both vapor and liquid fuel to the engine. This situation is often exacerbated by temperature changes, altitude variations, or low fuel levels that can increase the likelihood of vapor formation.

In contrast, other options do not directly correlate with the symptom of fluctuating fuel pressure. While a failing fuel pump could potentially cause pressure instability, it typically results in a steady drop in pressure rather than fluctuations. An empty fuel tank would usually lead to a lack of pressure, not fluctuations. Clogged fuel lines may restrict flow and create a steady drop in pressure rather than erratic fluctuations as the pump encounters intermittent blockages. So, the presence of rapid fluctuations strongly suggests the occurrence of vapor formation in the fuel system.