Urns for travel? Yes, apparently the exist. The other day I was talking with some clients, and the husband told his wife "when I die, I want my remains scattered in Columbia...the country. And they have special urns for flying." My ears perked up -- they do?
The situation has never presented itself to me before, but I know that travel is never easy. Add in a metal container, sealed, containing human remains and all of a sudden you have an airport nightmare.
Based on a quick Google search, it appears that what is currently advised is to use a travel urn or container, something made from plastic or wood, that can be x-rayed. Metal cannot be x-rayed, and you run the risk of not being allowed to take the item on board.
For up-to-the-minute laws and regulations, it is best to check with TSA or call 1-8660289-9673. Using the agency's search engine (look for the "can I travel with" button), each airline may have its own policy as well.
Remember, a blog is not legal advice. Please speak with an attorney for counsel specific to your situation.