What type of flight is primarily indicated when passengers are not present on board?

The type of flight primarily indicated when passengers are not present on board is a ferry flight. This type of operation usually involves repositioning an aircraft without any passengers onboard, often to relocate it to another airport for maintenance, to pick up passengers, or to reallocate fleet resources.

Ferry flights serve specific operational needs, such as moving the aircraft back to its home base or to a maintenance facility after repairs. This distinguishes them from cargo, commercial, or private flights, where the purpose typically includes the transportation of goods, a pre-scheduled flight for passengers, or specifically licensed personal travel, respectively. Therefore, the focus on ferry flights lies in their unique function of repositioning the aircraft without any passengers.