Definition
A regulatory weather minimum applied to certain Part 91 IFR takeoffs and to alternate airport planning, requiring at least a 600-foot ceiling and 2 statute miles visibility for airports with precision approaches, or an 800-foot ceiling and 2 statute miles visibility for airports with only non-precision approaches. The numbers represent the standard alternate minimums under 14 CFR 91.169 unless the approach chart specifies otherwise.
Plain English
When picking an alternate airport for an IFR flight, the forecast at your estimated arrival time must show clouds no lower than 600 feet and visibility no less than 2 miles if the airport has a precision approach, or 800 feet and 2 miles if it only has a non-precision approach. These are the default numbers; some airports list different values on the approach chart.
Context Anchor
Seen during IFR flight planning under Part 91, when deciding whether an airport is legal to list as your alternate.
Derivation
The numbers are aviation weather shorthand. In “600-2,” the first number means a 600-foot ceiling and the second number means 2 statute miles visibility. In “800-2,” the ceiling changes to 800 feet while the visibility stays 2 statute miles.
Why Pilots Care
It gives general aviation pilots a legal, safe way to depart IFR when commercial operators would be grounded by higher minimums.
Intuition Check
Do not treat 600-2 and 800-2 as landing minimums or destination weather minimums. They are planning minimums for the alternate airport when an alternate is required.
Example Sentence 1
The forecast for the alternate showed 1,500 broken and 5 miles visibility, well above the 600-2 rule, so the pilot listed it on the IFR flight plan.
Example Sentence 2
The single-engine aircraft waited for conditions to reach 800-2 before the pilot accepted the IFR clearance.