Oops, sorry to have been so uninformative.

Flights are on 755s SEA-MEM more than 7 days out.

When I started this thread, I'd been considering using miles for upgrades, since CO's website shows the SEA-MEM leg using WBC-equipped 747-200. Further checking on nwa.com shows equipment as 755. Drat!

You'd think CO and NW would coordinate schedule info a bit better, wouldn't you? :s