Hello, and welcome.
My apologies that no one had answered your question earlier. Various experts are online at different times and I recently logged in and was notified of your question. Your patience is appreciated! I actually answered your question about an hour ago, but then 'edited' to add more information, so the time of the latest edit is shown on the time of the answer.
My heartfelt condolences on your loss.
Some metal urns return an opaque image when going through x-ray (yes, it will need to go through x-ray at security), so the TSA recommends that you purchase a temporary container made of wood, plastic or non-lead lined ceramic for transporting your husband's remains as carry-on, so the contents can be seen and cleared on x-ray; then, they can be transferred into the brass urn for burial. Your local funeral home can usually help you with purchasing a temporary container.
Please keep in mind that out of respect, no TSA security screener will ever open the urn or container, even if you ask them to, to prove all it contains is crematory remains.
You can read more, here:
I hope this helps and wish you safe travel.
Please be so kind as to rate my answer with positive feedback; that is the only way I receive recognition from the site for my assistance. Thank you very much!
Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply' for clarification or additional information, if needed, and I will be glad to continue.