All lithium batteries have a chance to leak, or explode. If you charge them correctly and NOT in a USB port, if you carry them in your pocket or purse in their OWN CASE the chances are much slimmer they will fail. If your battery allows for a cartomizer to fit on top then NEVER transport it without a cartomizer on top! And always turn your spare battery OFF while transporting it. Remember one thing when flying, fire needs oxygen. Don't give it any! Turn your battery off and encase it and then put it in a zip lock bag. Be safe!