Originally Posted by
olddog
And Black Flag (Black in modern usage) - Airfield unusable for reasons other than weather. Eg blocked runway due to incident.
A Black Flag Day was normally a weathered out day. The runway being declared Black was normally an aircraft stuck on it i.e in the RHAG, etc. But I have heard them being called Black due to ice, snow, etc.
Always under the impression the reason for a runway being declared Black was that it was unusable for absolutely *any* reason.