When is an aircraft most likely to stall?

An aircraft is most likely to stall during a steep climb due to the angle of attack exceeding the critical value. The angle of attack is the angle between the wing’s chord line and the oncoming airflow. In a steep climb, the relationship between the aircraft’s pitch attitude and the available lift can result in the airflow separating from the wing, causing a loss of lift. This is particularly true in a steep climb because the aircraft is attempting to gain altitude while generating the necessary lift at a higher angle of attack.

In contrast, at high speeds, the airflow over the wings is stronger, which can help maintain lift even at higher angles of attack, making a stall less likely. When flying straight and level, the aircraft operates within a stable environment, typically below the stall angle of attack, thus minimizing the chances of stalling. High humidity does not have a direct effect on stall occurrence; rather, it may influence lift or drag characteristics subtly, but not to the extent that it would cause a stall compared to the dynamics present in a steep climb.