The provision to operate 1,000 feet-on-top exists so that separation restrictions normally applied by ATC can be temporarily suspended. 1,000-ft-on-top IFR flight may be conducted provided that
- The flight is made at least 1,000 ft above all cloud, haze, smoke, or other formation
- The flight visibility above the formation is at least three miles
- The top of the formation is well defined
- The altitude appropriate to the direction of flight is maintained when cruising in level flight
- The “1 000-ft-on-top” flight has been authorized by the appropriate ATC unit
- The aircraft will operate within Class B airspace at or below 12,500 ft ASL, Class C, D, or E airspace.
NOTE: ATC does not apply separation to aircraft operating 1,000-ft-on-top except in the following conditions:
- At night, separation is applied between an aircraft operating 1,000-ft-on-top and other aircraft if any of the aircraft are holding
- Between aircraft operating 1,000-ft-on-top and an aircraft operating on an altitude reservation approval.
REFERENCES
AIM RAC 8.7 1,000 Feet on Top IFR Flight