Do not use Mode C to effect vertical separation with an aircraft on a cruise clearance, contact approach, or as
specified in paragraph 5-14-4, System Requirements, subparagraph f3.
Assign an altitude to an aircraft only after the aircraft previously at that altitude is observed at or passing
through another altitude separated from the first by the appropriate minima when:
Severe turbulence is reported.
Aircraft are conducting military aerial refueling.
The aircraft previously at that altitude has been issued a climb/descent at pilot's discretion.
EN ROUTE. When the position symbol associated with the data block falls more than
one history behind the actual aircraft target or there is no target symbol displayed, the Mode C information in
the data block must not be used for the purpose of determining separation.
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