Landing minimums are the minimum weather conditions required to continue and complete an instrument approach for landing. They are found on the approach chart and in the operator’s OpSpecs. For Part 121, the FAA says a pilot may not continue past the FAF, or begin the final approach segment, unless the latest weather report shows the visibility is at or above the minimum visibility prescribed for that procedure.

Alternate minimums are different. They are used during dispatch planning to decide whether an airport is legal to list as an alternate. Under Part 121, an airport cannot be listed as an alternate unless weather reports or forecasts show the weather will be at or above the alternate weather minima specified in the certificate holder’s OpSpecs when the flight arrives.

When to use alternate minimums?

Anytime you are selecting an alternate for planning purposes. (Takeoff alternate, destination alternate, enroute alternate, ETOPS alternate)

Alternate minimums are 600-2, 800-2 (or 1 NAV, 2 NAV rule).

When to use landing minimums?

You cannot dispatch to destination which is below “landing minimums” at ETA.

So what’s is 1-2-3? That’s just to determine if you are require by law to plan alternate for your destination. Nothing else.

Landing minimums = can I legally fly this approach and land now?

Alternate minimums = can I legally list this airport as my backup during dispatch planning?