<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by number_6:
For BA the sequence is BA Premier, BA Gold, Emerald, BA Silver, Sapphire and only then BA Blue.</font>
I think you've missed out OW Ruby in there. I guess they come ahead of BA Blue also since they are earned status levels on most of the OW airlines except BA (e.g. CX Silver)