What defines a "Direct Flight"?

A direct flight is defined as a flight that operates between two cities without any stops, meaning passengers remain on the same aircraft throughout the journey. This includes instances where the aircraft does not change but may include a stop in between for refueling or other operational reasons without requiring passengers to change planes. Therefore, the definition effectively captures the essence of a direct flight, as it highlights the continuity of travel despite any landing or operational pause.

Understanding this definition clarifies why other options don't align with the concept of a direct flight. A flight that operates without any stops accurately reflects a non-stop service, while a layover implies a change in aircraft or a transfer that is not characteristic of a direct flight. The focus on in-flight services does not pertain to the definition of a direct flight as it concerns operational procedures rather than the nature of the flight itself.