I searched the forums and didn't find this particular rendition of the macro. What this one does is tests if you can use a flying mount and if you can will use it. Otherwise it will use the land mount.
I found the flyable modifier on wowwiki after getting tired of switching mounts.
#showtooltip Amani War Bear
/cast [nocombat, nomounted] Crusader Aura; [mounted] Concentration Aura;
/stopcasting
/cast [flyable, nomounted, nocombat] Swift Purple Windrider; [nocombat, nomounted] Amani War Bear;
/dismount