As a general rule, you are allowed to take cremated remains with you on an airplane. However, you must consider airline regulations, TSA policies, and local laws before you plan to fly.
The regulations for transporting an urn on an airplane depend on the specific airline you intend to use. Well in advance of your flight, contact the airline directly to ask about its policies. Some airlines will only permit you to transport an urn in checked baggage. Others require that you carry the urn into the cabin with you, and not put it in your checked baggage. In either case, the urn should be sift-proof and have no chance of leakage or accidental opening during the flight.
It is the policy of the Transportation Security Administration (TSA) to never open an urn under any circumstances. As a result, you are obliged to follow TSA rules for urns that you intend to take through security. Give yourself plenty of time to go through security, just in case you have a longer wait for approval. Bring a copy of the death certificate or certificate of cremation as verification of the urn’s contents. The TSA recommends that you use a lightweight container that seals tightly and will not easily come open. The urn will be sent through the scanner, which will not damage the urn or the ashes in any way. If the urn is made of a material (such as lead) that makes the image opaque, the TSA agent may request further screening or refuse permission to take the item on board. However, modern urns made of such materials are unusual.
Your plans to dispose of the ashes may require your additional consideration. Before you travel, contact a local funeral director for advice about transportation. You should also talk to a funeral director in the area to which you are going to ask about local laws and regulations. This is particularly important if you plan to take the ashes out of the country.
Transportation of ashes by plane may be done fairly easily if you plan ahead. Follow the rules set by the airline, TSA and your destination, and you will arrive with the urn and ashes safe and sound.