As a frequent business class international traveler I am really frustrated that I cannot use my over 600,000 plus miles the way that I want. I sure wish Delta Airlines would allow Diamond Medallion members, well anyone really, to book an international flight with miles and to also upgrade with miles. I am equally frustrated that I cannot book an international flight with miles and use my system wide upgrade certificates. I sure like Air New Zealand approach of using miles as mile per dollar. Maybe I need to switch to Singapore Airlines.