How do you transport someone's cremains legally from one place in the US to another across many states without driving?

Licensed funeral homes usually handle the transportation of cremains or bodies when it pertains to civilians. However, when it concerns cremains (bone fragments from cremation) it is generally accepted that the deceased survivors may dispose of or transport them in any manner that does not affect health laws or endanger the public safety. Funeral homes are usually in charge of making arrangements with an airline either commercial or private to transport cremains and/or bodies.