What is meant by "straight and level" flight?

"Straight and level" flight refers to the aircraft maintaining a constant altitude while flying in a straight path without any turns. This means that the pilot is managing the aircraft's pitch, roll, and yaw so that it is neither climbing nor descending, and also not changing its directional heading.

In this state, the aircraft's lift is equal to its weight, and its thrust is equal to its drag. This level flight is crucial for maintaining stability and ensuring that the aircraft is in a controlled state. It is the basis for performing various maneuvers and managing the aircraft in different phases of flight, such as cruising.

The other options do not accurately describe "straight and level" flight. Flying in a straight line only would not include the requirement for constant altitude, while ascending steadily or descending gradually involves changing altitude, which contradicts the definition. Thus, maintaining a constant altitude and heading captures the essence of what "straight and level" flight means in the context of piloting an aircraft.