Under what condition should a pilot on IFR advise ATC of minimum fuel status?

Advise ATC of minimum fuel status when the remaining fuel precludes any undue delay. This means that if a pilot becomes aware that their fuel levels are getting low enough that even small delays could lead to a situation where they might not have enough fuel to reach their destination safely, they should communicate this status to ATC. This is important because it allows air traffic controllers to prioritize the aircraft's landing or provide necessary routing adjustments to prevent potential fuel exhaustion.

This consideration takes into account that safe aviation operations depend not just on the quantity of fuel but also on the operational pressures the pilots may be facing. It helps ensure that the pilot can maintain safety while also being integrated effectively into the air traffic system, which may require prompt action on the part of ATC to assist the pilot in managing their flight.