Define "glide slope."

The term "glide slope" refers specifically to the vertical descent path that an aircraft follows as it approaches a runway for landing. This path is crucial for pilots as it helps them align their descent with the runway at a safe and optimal angle. The glide slope is a key component of the Instrument Landing System (ILS), allowing for precision in landing, particularly in low visibility conditions. By maintaining the correct glide slope, pilots ensure that they reach the runway threshold at an appropriate altitude and configuration, which is essential for a safe and effective landing. This concept differs significantly from the other choices, which relate to different phases and aspects of flight, such as takeoff trajectory, in-flight altitude maintenance, or ascent angles.