We used Continental a few months ago, taking ashes to their final resting place on the East Coast. The Crematorium packaged them with a TSA-friendly container, we took the Cremation certificate and the death certificate, and there was absolutely no problem.

A big thank you to everyone who has posted on FlyerTalk in the past. A search here gave me all the information I needed, and made the experience much less stressful and miserable than it could have been.