Which factor increases the probability of stall in an aircraft?

The probability of a stall in an aircraft increases with an excessive pitch angle because it directly affects the angle of attack of the wing. The angle of attack is crucial in determining the lift generated by the wing. When the aircraft's pitch is raised significantly, the angle of attack can increase beyond the critical angle, where the airflow over the wing begins to separate. This separation leads to a loss of lift and can result in a stall. Understanding that the relationship between pitch angle and lift is key to managing aircraft performance is essential for safe flying practices.

In contrast, while high airspeed during turns and low wing loading are factors related to aircraft performance and handling, they do not inherently increase the likelihood of a stall in the same direct manner as an excessive pitch angle does. Flat turns at high altitude may influence stall dynamics, but they are more complex as they depend on a range of other factors, including the aircraft's design, load distribution, and environmental conditions.