No offense, as you may be the exception, but most smokers' sense of what smells and does not - especially as it relates to tobacco-related odors - is very much weaker than those of us who do not smoke.

I've never been around e-cigs, but I have been around folks using a marijuana vaporizer, and that one definitely smelled. Just not as badly as smoke.

Further, if the vapor emitted goes anywhere except directly into the smoker, it's still exposing those around to it, and in an airplane (because it's a very enclosed space with a lot of strangers and poor air replacement rates), that's still entirely inappropriate.