Most airlines will allow you to transport cremated remains, either as air cargo, or as carry-on or checked luggage (traveling with you). You should check with the airline to determine their exact policies on either shipping or handling as luggage, and make sure the contents are identified as cremated remains. You will also need to review the Transportation Security Administration requirements.
You should also consult a licensed funeral director at both the point of departure and the destination to find out if there are any local laws that need to be observed as well. Arrive early in order to pass through security clearance, and carry the death certificate, certificate of cremation, and any other relevant documents with you.