What must a pilot confirm before starting an IFR flight?

Before starting an IFR flight, it is essential for a pilot to confirm the completion of flight data and weather briefing. This step ensures that the pilot has gathered all necessary information regarding the route, weather conditions, and any potential issues that could affect the flight. A thorough briefing provides critical insights into not only current weather and flight conditions but also potential changes throughout the duration of the flight, which is particularly vital under Instrument Flight Rules (IFR) where reliance on instruments becomes paramount due to potentially reduced visibility.

Other aspects of the flight preparation, while important, do not hold the same level of necessity in the context of IFR operations. For instance, notifying passengers of flight duration is certainly courteous and enhances passenger expectations but does not directly influence safety and operational preparedness. Maintaining a valid medical certificate is a crucial part of a pilot's overall compliance with regulatory standards, but it is assumed to be in place for any flight operations. Lastly, while flight crew verification is vital in ensuring team coordination and safety, it may not be strictly required for each individual pilot when flying solo. Therefore, the focal point for an IFR flight is the thorough completion of flight data and weather briefing to guarantee informed decision-making throughout the flight.