Several pilots that know what I do sent this article to me. It is an excellent example why you should not try scattering ashes on your own from an airplane, and why you should not ask a pilot friend or family member to try this for you:
https://www.avweb.com/insider/a-brief-history-of-dispersals-over-iowadahos-wilderness/
When I tell other pilots what I do, I almost always get to hear their stories about what happened to them or to a pilot they know when they attempted to scatter ashes from their airplane. The story usually goes something like this: “Oh, I tried that once for a family member. We opened the bag of ashes, stuck it out the window, and all the ashes came right back in on us”. And even more tragic, sometimes the loved one of the deceased is in the plane with them, and they get covered with the ashes too. Even worse, because the ashes do have some mass and grit to them, they can damage the paint and control surfaces of the plane as they swirl out. And if you accidentally let go of the bag, it can stick to the stabilizer or rudder. Most pilots were not aware of the forces at play or the potential complications, so the attempted scattering ended in a memory they did not want but are happy to share with me.
Please do not try to scatter the ashes of a loved from an airplane if you have not done it before. It will most likely go badly and that will be the memory you and their loved ones will have forever. Please hire a professional or talk to a professional beforehand. We want your memories of this important event to be good ones. When done properly, scattering the ashes from an airplane of your loved one will be a beautiful memory.