Which situation requires immediate notification to the NTSB?

Immediate notification to the NTSB is required in situations involving accidents or if a crew member cannot perform their duties. An accident is defined as an event that results in significant damage to the aircraft or injury to persons on board or on the ground. In this context, a failure of a crew member to perform their duties could jeopardize the safety of the flight and, as such, must be reported promptly to the NTSB so they can investigate and address any safety implications.

The other scenarios listed do not necessitate immediate notification. Changes in a flight plan may be communicated to relevant air traffic control but do not need to be reported to the NTSB unless they result in an accident. Minor turbulence is a normal part of flying, so it does not require any formal reporting. Similarly, a flight delay due to weather is common and wouldn't trigger an NTSB notification, as it doesn't impact the safety of the flight in the same way an accident or crew issue would. This emphasizes the importance of distinguishing between normal operational disruptions and safety-related events that warrant immediate attention from regulatory bodies.