All major airlines have been rigorously promoting low cost air fares for all kinds of air travel, and this has substantially helped in increasing their market penetration, and has made air travel affordable for many more people. People addicted to smoking would obviously like to fly these airlines along with their e-cigarettes.
Since e-cigarettes are battery operated, they are categorized as an electronic device (like laptops, mobile phones etc.) and thus have to go through a very strict security check at the airports. These security checks have become even stricter in the U.S since 9/11 happened. Though people in the U.S are still familiar with e-cigarettes, there are many countries where they are not marketed that aggressively, and people have not seen a lot of them. As a result, there have been instances reported where an e-cigarette was mistaken by the security personnel for a pen gun, and consequent confiscation. This caused a lot of inconvenience and wastage of time to the individual concerned. The fact that these things SAVE lives should be more reason to allow them everywhere in my opinion.
Though the Transportation Security Administration Guidelines do not specifically mention any limitations on carrying e-cigarettes, they do have certain rules to be followed for carrying lithium batteries (which is a part of the e-cigarette). These rules, however, are not very stringent. Even then, it is always advisable to study these rules and regulations before you decide to carry an e-cigarette with you in an aircraft, because you definitely do not want to be harassed for something that could have been avoided easily. As a backing, you can always carry a copy of the user guide of the e-cigarette or a copy of the purchase bill.
Since there are certain rules pertaining to carrying liquids on an aircraft, you need to be cautious about carrying the e-liquid as well, which needs to be refilled in the cigarette. Though it not a necessity, but it is always a safer bet to declare the presence of the e-liquid at the time of the security check, even if the security personnel do not ask you for it specifically.
If you are caught up in some trouble even after taking care of all these factors, a good idea would be to keep your e-cigarette in a personalized packet and leave it with the security personnel. This would save you the disappointment of having to throw it away in a bin just because you couldn’t carry it along. This wastage of money is definitely not something that you would want at the start of your trip.
One last word of caution is to be careful about where you smoke your e-cigarette. The most probable situation is that smoking it would not be allowed on board the aircraft, and thus you would need to visit a smoking lounge or any other designated smoking area to avoid all the trouble. Just because it is an e-cigarette and not a traditional cigarette does not mean that you would be able to smoke it even where smoking is not permissible.
Be safe and travel smart !