Final answer:
To maintain altitude at a slower airspeed, the angle of attack must increase.
Step-by-step explanation:
In order to maintain altitude at a slower airspeed, the angle of attack must increase.
The angle of attack refers to the angle between the wing's chord line (a straight line drawn from the leading edge to the trailing edge) and the oncoming air. By increasing the angle of attack, the wing can generate more lift even at a slower airspeed, allowing the aircraft to maintain altitude.
For example, when an airplane is landing, the pilot increases the angle of attack to generate more lift and maintain altitude at a lower speed.