You may clear an aircraft to maintain “VFR-on-top” if the pilot of an aircraft on an IFR flight plan requests the clearance.
1. When an aircraft has been cleared to maintain “VFR-on-top,” the pilot is responsible to fly at an appropriate VFR altitude, comply with VFR visibility and distance from cloud criteria, and to be vigilant so as to see and avoid other aircraft. The pilot is also responsible to comply with instrument flight rules applicable to the flight (e.g., adherence to ATC clearances).
2. Although IFR separation is not applied, controllers must continue to provide traffic advisories and safety alerts, and apply merging target procedures to aircraft operating VFR-on-top.
You may clear an aircraft to climb through clouds, smoke, haze, or other meteorological formations and then to maintain “VFR-on-top” if the following conditions are met:
The pilot requests the clearance.
You inform the pilot of the reported height of the tops of the meteorological formation, or
You inform the pilot that no top report is available.
When necessary, you ensure separation from all other traffic for which you have separation responsibility by issuing an alternative clearance.
When an aircraft is climbing to and reports reaching “VFR-on-top,” reclear the aircraft to maintain “VFR-on-top.”
CLIMB TO AND REPORT REACHING VFR-ON-TOP,
TOPS REPORTED (altitude),
NO TOPS REPORTS.
IF NOT ON TOP AT (altitude), MAINTAIN (altitude), AND ADVISE.
Do not clear an aircraft to maintain “VFR-on- top” between sunset and sunrise to separate holding aircraft from each other or from en route aircraft unless restrictions are applied to ensure the appropriate IFR vertical separation.
MAINTAIN VFR-ON-TOP AT OR ABOVE/BELOW/BETWEEN (altitudes).
“Maintain VFR-on-top at or above one three thousand five hundred.”
“Maintain VFR-on-top at or below one two thousand five hundred.”
“Maintain VFR-on-top at or between six thousand and one zero thousand.”
When, in your judgment, there is reason to believe that flight in VFR conditions may become impractical, issue an alternative clearance which will ensure separation from all other aircraft for which you have separation responsibility.