JUULpods are best taken in carry on. Exposure to extreme altitude changes can cause e-liquid leakage in JUULpods, especially if they're partially used. You should dispose of partially used JUULpods before you get on a plane and use a fresh one when you land.
JUUL Devices are safe for travel, but most airlines restrict the use of e-cigarettes and vapourisers. The Portable Charging Case is also safe for travel, but most airlines have restrictions for lithium batteries. So, always double check the list of prohibited items with the airline company you are travelling with.