What is necessary for block time to be accurately recorded?

For block time to be accurately recorded, it is essential that the brakes are released or the passenger door (PAX door) is shut. Block time refers to the total time from when an aircraft leaves the gate until it arrives back at the gate, which includes all ground movements as well as the flying time.

Releasing the brakes or closing the passenger door signifies that the aircraft is ready for taxiing, indicating the beginning of the block time. This ensures that all time spent on the ground prior to takeoff and after landing is accurately included within the block time measurement. If the brakes are set, it implies that the aircraft is stationary and not yet at the point of departure from the gate or taxiway, which does not accurately reflect the block time.

In contrast, the options regarding the aircraft being airborne or having left the ground pertain to different phases of flight but do not address the critical prerequisites for initiating the block time. Therefore, the correct condition for accurately recording block time is indeed the release of the brakes or the shutting of the PAX door.