What is one common cause for a delayed flight?

A common cause for a delayed flight is mechanical issues. Airlines prioritize the safety and operational efficiency of their aircraft, so when a mechanical problem is detected, the flight is often delayed while the issue is addressed. This could involve routine maintenance checks or repairs to systems and components necessary for safe flight operation.

On the other hand, while factors like weather and passenger loading can influence flight schedules, they are not as directly related to the immediate operational status of the aircraft itself. For instance, though monsoon weather can affect flight schedules significantly, it introduces delays through external conditions rather than internal aircraft readiness. Similarly, while available seating and passenger loading can complicate logistics, they do not directly prompt the need for an aircraft delay in the same way that mechanical issues do. Thus, mechanical problems represent a clear and common reason for a flight delay due to their direct impact on flight safety and airworthiness.