Since my last post, my family member has successfully taken his AED on a commercial flight. He was not allowed to bring the device in to the cabin, but had to bring the lithium ion battery in his carry on. Therefore he needed to run back to the airline desk and have his luggage pulled out and get the AED into his checked luggage. This held him up quite a bit at TSA, so plan ahead and arrive early. I believe that these rules are administered differently at different airports, as I was even advised when researching in advance that "it would depend on the TSA officer on duty." Hopefully someone will be able to get clear advice on this, but for now I would advise: check the device and carry the battery.