Define the term "cruise flight."

Cruise flight is defined as a state of flight where an aircraft maintains a constant speed and altitude, allowing for efficient and stable operation over longer distances. This phase of flight is essential because it maximizes fuel efficiency and minimizes pilot workload, as the conditions remain relatively stable compared to ascent or descent phases. During cruise, the aircraft's lift balances its weight, and thrust balances drag, allowing it to fly smoothly in a straight line, which is crucial for long-range travel.

The other options describe different flight scenarios that do not accurately depict the characteristics of cruise flight. For example, constant changes in altitude indicate a climb or descent rather than a steady cruise. A high-speed descent towards the runway is part of the approach phase rather than cruise. Lastly, a maneuver involving steep turns pertains to dynamic flight operations and would not fit the definition of maintaining a constant speed and altitude.