Final answer:
A Pilot in Command must not deviate from the instructions in an ATC clearance unless there is an emergency or a TCAS resolution advisory. Maintaining adherence to ATC instructions is critical for air traffic safety, and any exceptions must be communicated to ATC as soon as feasible.
Step-by-step explanation:
When ATC clearance has been obtained, no Pilot in Command (PIC) may deviate from the instructions provided by air traffic control (ATC) unless they have received an amended clearance. The only exceptions to this are in an emergency situation or if the deviation is in response to a traffic alert and collision avoidance system (TCAS) resolution advisory.
Following clearance instructions is crucial for maintaining the safety and efficiency of air traffic control systems. Deviating from an ATC clearance without proper authorization could lead to dangerous situations such as traffic conflicts or breaches of controlled airspace. Therefore, it's imperative that the PIC adheres to ATC guidance unless exceptional circumstances arise.
If an emergency occurs that requires immediate action, the PIC is authorized to make the necessary changes to the flight path or altitude to ensure the safety of the flight. In such cases, the PIC is required to notify ATC of the deviations as soon as possible.