Originally Posted by
aacharya
I think you have to lump into two categories:
Lifetime levels (Million Miler, etc)
Annual levels (CO*, United GS, etc)
What you probably are looking after are the CO* and United GS-type levels.
CO*'s are pretty impressive to me (they are almost automatically CO Plats).
In my opinion one of the hardest to obtain, based on annual levels and not on revenue or "by invitation only" is the Lufthansa HON Circle. You need to accrue 600.000 HON qualifying miles in two years.