For an IFR flight plan with multiple legs at different altitudes, what altitude should be specified for the cruising level?

For an IFR flight plan that encompasses multiple legs at different altitudes, the cruising level specified should be the altitude for the first leg. This is because the flight plan is filed based on the initial segment of the flight, and air traffic control needs to know the altitude at which the aircraft will operate during that initial phase. By providing the altitude for the first leg, you ensure that air traffic control is aware of the aircraft's intended trajectory from the start of the flight, which is critical for maintaining safety and separation from other air traffic.

The other options, such as an average cruise altitude, the highest altitude, or the lowest altitude, may not accurately represent the initial phase of flight and could lead to confusion or miscommunication with air traffic control. Specifically, using an average could misrepresent the initial operational altitude, while stating the highest or lowest altitude does not provide the necessary information for the start of the flight. Thus, specifying the altitude for the first leg maintains clarity and aligns with standard flight planning practices.