Visual separation may be applied between aircraft up to but not including what altitude?

• A. FL100
• B. FL180
• C. FL200
• D. FL250

Answer: (B)

Visual separation can be applied between aircraft in controlled airspace under specific conditions, primarily based on altitude. The correct answer, which specifies that visual separation can be maintained up to but not including FL180, reflects the altitude limitation where this separation method is permissible.

At altitudes below FL180, air traffic controllers can ensure that aircraft are separated visually, allowing them to maintain safe distances apart while providing a more flexible air traffic flow. However, this method becomes increasingly challenging and less reliable as aircraft climb higher. Above FL180, the FAA (Federal Aviation Administration) requires more stringent separation standards, which typically involve vertical and horizontal separation rather than relying on visual observation between pilots and controllers.

This means that for the safety and efficiency of air traffic management, visual separation is officially recognized and allowed only below this threshold. Thus, option B accurately identifies the altitude limit, ensuring that pilots and air traffic controllers can apply this separation method effectively within its operational parameters.