Which element is NOT one of the four main elements that affect risk during a flight?

The element that is not one of the four main elements affecting risk during a flight is the time of day. The four primary elements that typically influence risk include the pilot, the aircraft, the environment, and external pressures.

The pilot represents the decision-making capabilities and experience level, both of which directly affect flight safety. The aircraft involves its mechanical condition, performance capabilities, and familiarity with its systems. External pressures may include factors such as time constraints, passenger expectations, or other situational demands that could lead to poor judgment or rushed decision-making.

While the time of day can have effects (like visibility at night or during dawn/dusk), it does not consistently represent a fundamental risk element relative to the pilot, aircraft, and environmental pressures that fundamentally shape the safety and decision-making framework in aviation. This makes time of day an aspect that can influence certain operations but not a main constituent in the risk assessment model used for safe flight operations.