What is the altitude change reporting requirement when operating VFR on top?

When operating VFR on top, the requirement is to report when vacating a previously assigned altitude. This is important because it allows air traffic control to maintain safe separation between aircraft flying at different altitudes. VFR on top refers to operating under Visual Flight Rules while above a layer of clouds, and maintaining communication with ATC is crucial for ensuring a safe airspace environment.

By reporting when leaving an assigned altitude, pilots help ATC manage traffic more effectively, especially since there may be aircraft operating under Instrument Flight Rules (IFR) at lower altitudes. This accountability is essential for situational awareness, providing both the pilot and ATC with necessary information to prevent conflicts and ensure safety in the sky.

The other options misrepresent the requirements: reporting every 2,000 feet or changes of 500 feet is not standard for VFR on top, and simply reporting any change can lead to unnecessary communication without the critical context needed for airspace management.