Yes, in most cases you may bring e cigarettes and vape devices on flights, but almost always only in your hand luggage or on your person, not in checked baggage. TSA, FAA, IATA and EASA all state that e cigarettes belong in the cabin because they contain lithium batteries that may pose a fire risk.
The most important rule is therefore simple: never put your e cigarette in a suitcase that is checked in. The reason is that incidents involving lithium batteries are easier to detect and deal with in the cabin than in the hold, where the crew cannot intervene in the same way. The FAA also emphasises that the device must be protected against accidental activation during transport.
That does not, however, mean that you may use it on board. On the contrary, vaping on flights is prohibited. It is expressly forbidden to use e cigarettes on commercial flights where smoking is prohibited. You should also not charge your e cigarette on the plane.
To travel more safely, you should pack the device so that it cannot be switched on by mistake. This may mean turning it off completely, locking the button if the model has a locking function, and protecting any loose batteries against short circuit. IATA also states that spare batteries must be individually protected in hand luggage.
Brief information
You can therefore usually bring an e cigarette on a flight, but only in your hand luggage, never in checked baggage. You must not use or charge it on board, and you should pack it so that it cannot be activated by mistake. The safest rule of thumb is: keep the device close to you in the cabin, keep the battery protected, and check the airline’s rules before departure.