A flight shall not be continued towards the aerodrome of intended landing, unless the latest available information indicates that at the expected time of arrival, a landing can be effected at that aerodrome or at least one destination alternate aerodrome, in compliance with the operating minima established by the operator.
An instrument approach shall not be continued beyond the outer marker fix in case of precision approach, or below 300m (1000ft) above the aerodrome in case of non-precision approach, unless the reported visibility or controlling RVR is above the specified minimum.
If, after passing the outer marker fix in case of precision approach, or after descending below 300m (1000ft) above the aerodrome in case of non-precision approach, the reported visibility or controlling RVR falls below the specified minimum, the approach may be continued to DA/H or MDA/H. In any case, an aeroplane shall not continue its approach-to-land at any aerodrome beyond a point at which the limits of the operating minima specified for that aerodrome would be infringed.
Note: Controlling RVR means the reported values of one or more RVR reporting locations (touchdown, mid-point and stop-end) used to determine whether operating minima are or are not met. Where RVR is used, the controlling RVR is the touchdown RVR, unless otherwise specified by State criteria.
Source: ICAO Annex 6