I've never heard of a flight being "sponsored" by another airline. There are NW-coded AS "operated" flights, however.

LAX-YVR is served nonstop by two airlines: Alaska (AS) and Air Canada (AC).

AS also "operates" flights for AA and NW. If you buy a ticket from AA or NW on that route, you will be flying Alaska.

You can also buy the AC flights as UA codeshares.

But now for the real question: why in the world did you post this in the Continental Airlines forum?