For an emergency landing at KGWO, when is the strip considered deadwood?

The correct answer is that the strip is considered deadwood upon receipt of landing time from KGWO. In air traffic management, "deadwood" refers to an active flight plan that will not be carried out due to circumstances such as an emergency landing. When the aircraft in distress communicates its intention to land and provides the specific landing time, it indicates that other aircraft can no longer rely on that strip for their navigation or planning purposes. This marks a clear point where the situation changes from planned operations to emergency handling, rendering the use of the airspace for regular traffic infeasible.

Other options reflect different stages of communication or procedural transitions, but they do not convey the point at which the operational status of the strip is definitively altered to deadwood. For example, frequency changes, establishing communication, or notifying sectors are all parts of the overall emergency response process, but they do not result in the airspace being classified as deadwood. The receipt of the landing time is the definitive action that affects air traffic planning and priorities, thus confirming that the strip is unusable for additional traffic.