CO has no revenue upgrades.

The only ways to upgrade on a CO domestic flight are as follows:

1. Unlimited space-available upgrades for CO and NW elites based on elite stattus (plat, gold, silver), fare basis, and date of purchase of the ticket.

2. CO elites who purchase a full Y fare are automatically upgraded (assuming space is available in FC). All others will be upgraded at the airport if FC inventory is available

3. Award upgrades using ff miles

For international flights, the only option is using miles and paying a co-pay (this is only available to CO elites)