It is possible to upgrade on US flights for active employees as long as you have upgrade certificates in your account. It is $10 per certificate domestic and $100 I believe for international over 3000 miles. You have to pay in advance with a credit card but can refund it if you don't use it. I would think D2R would be eligible too but I'm not sure. On US domestic elites get free upgrades but not int'l. Don't really see too many revenue pax springing for a paid upgrade especially on a leisure route.