Correct. When determining if you'll be eligible to earn mileage credit in your AS Mileage Plan account, it's all based on the operating carrier, regardless of what your ticket says. In most cases, however, you'll still be able to earn AS MP credit on commuter flights, such as a DL commuter flight operated by SkyWest, although this does vary from partner to partner. Some partners also offer credit only on certain flight numbers, usually those operated by the mainline carrier. You'll find this alot with BA, KL, and QF. If you have a specific itinerary you wanted to run past me, let me know and I'd be happy to check on it for you.