Report leaving and report reaching go in which block on the strip?

The correct answer is that report leaving and report reaching go in space 20 with altitude restrictions. This is because space 20 on the flight progress strip is specifically designated for tracking the altitude of aircraft as they transition through different phases of their flight. When controllers receive reports from pilots about leaving a specific altitude or reaching another, it is imperative to record this critical information in this designated space to ensure accurate tracking of the aircraft’s vertical movements.

Recording the report leaving and report reaching in space 20 allows controllers to maintain a clear understanding of the aircraft's current and intended altitude, which is essential for managing air traffic safely and efficiently. This information is also vital for ensuring separation from other aircraft.

The other choices, while they refer to different aspects of the flight progress strip, do not pertain specifically to altitude reporting. Thus, they would not be appropriate for recording reports related to altitude transitions.