Is the ICAO base turn procedure mandatory to fly?

The correct choice correctly states that the ICAO (International Civil Aviation Organization) base turn procedure is optional rather than mandatory. ICAO provides guidelines and best practices for aircraft operations, but these guidelines are often implemented as recommendations rather than strict regulations.

Pilots may choose whether or not to utilize the base turn procedure based on various factors, including but not limited to the type of approach, the specific airspace or air traffic control directives, and the conditions of the flight. The situation and the discretion of the pilot, in accordance with established safety practices and regulations, dictate the use of the procedure. This flexibility allows pilots to adapt to varying conditions and operational requirements rather than adhere to a one-size-fits-all mandatory rule.

In contrast, the other options imply restrictions or conditions that do not capture the essence of the ICAO recommendations, which prioritize safety and efficiency without imposing mandatory compliance in every situation.