Which method of Traffic Management involves canceling all clearances?

The correct answer is ground stops, a method of traffic management that involves halting all departures from an airport. This procedure is typically implemented due to various safety concerns, such as adverse weather conditions, equipment malfunctions, or incidents affecting runway operations. By canceling all clearances, airports can manage traffic effectively to ensure safety and prevent congestion in the airspace.

In contrast, metering refers to regulating the rate of aircraft departures through timing adjustments to maintain safe spacing and control the flow into congested airspace. Traffic reroutes involve redirecting flights that are already in the air to avoid problematic areas, while sequencing involves arranging the order of arrivals and departures to enhance efficiency without completely stopping all traffic.