NOTE: This information is subject to change according to airline and government policies, so be sure to check any time you are traveling to make sure there haven't been any changes.
Pack Safe: Electronic Cigarettes, Vaping Devices
In general, if you don't know whether it is safe and/or legal to carry your e-cig, it's best to err on the side of caution and avoid any potentially awkward situations by just leaving your e-cig at home. Before carrying an e-cig on a plane, be sure to check the laws in both your departure and arrival destinations, as well as any regulations the particular airline may have on their website. If you're still unsure, either (A) leave your e-cig at home, or (B) carry an inexpensive device that you won't miss if it gets confiscated.
According to the FAA, e-cigs may not be placed in any checked baggage, and must be kept in a carry-on bag for the duration of your flight. You may not use your e-cig while aboard the plane, and most airports do not allow vaping except in designated smoking areas. Each airline can make its own choices as to whether or not they allow e-cigs on flights, so check with both the FAA and the airline itself before traveling.
When making international flights, make sure to check the status of vaping in your destination country. Some countries have banned e-cigs, and it would not be a very good vacation if you got detained for breaking the law once you arrived. Even when traveling within your own country, some cities have passed bans that do not apply to the rest of the country, so above all be careful and don't get yourself into trouble. The last thing you need is to be arrested for vaping, and it wouldn't be good for the vaping community overall either due to bad publicity. So please, be smart and make 100% sure that you're doing the right thing before taking an e-cig on any trips.