Which action is typically taken to ensure the aircraft's systems are functioning properly before flight in the Warrior PA-28A?

Performing a thorough pre-flight inspection is a critical action taken to ensure that the aircraft's systems are functioning properly before flight in the Warrior PA-28A. This inspection involves checking various components and systems of the aircraft, such as the control surfaces, fuel levels, oil levels, tire pressure, and the condition of the flight instruments. The primary aim of this comprehensive assessment is to identify any abnormalities or issues that could affect safety and performance during the flight.

By conducting this inspection, the pilot can ensure that the aircraft is in airworthy condition and ready for operation, thus adhering to safety protocols outlined by aviation regulations. Additionally, pre-flight inspections help pilots become familiar with the aircraft's systems, which can enhance overall situational awareness and preparedness for the flight.

While actions like checking weight and balance, calculating estimated time of arrival, and checking passenger baggage weights are important for flight planning and safety, they do not directly address the immediate and essential need to verify the operational readiness of the aircraft itself. Therefore, the thorough pre-flight inspection is the most appropriate choice in this context.