Ok, heres the deal while vaping inflight coming from my own personal experience as a Cabin crew member. 90% of the time, I and my colleagues work Long to Ultra Long Haul International Flights (Flights ranging from 6-15 hours in duration)
At this time, there is no formal regulations regarding personal vaporizers and their use onboard passenger aircraft from the FAA, or TSA. All standard liquid rules do sill apply however (Less than 3ounces or 100mls, all fitting in a 1 quart clear plastic ziploc bag)
For the batteries, most airlines (Mine included) have regulations in place prohibiting Lithium Ion Batteries in checked luggage. Keep your batts in your carry on with you. They will not be confiscated by TSA.
As far as the PV itself... that is left up to the individual airline.
Most airlines that have restrictions on PV's will state so in their inflight magazine. Even if airlines do not state clearly whether or not PV use is allowed, it would be up to the flight attendants and captain. If you ask if using your PV is allowed, you just may get a miserable crew member that doesnt know what it is, and get a firm NO... or you may get their blessings as long as you are not disturbing other passengers. What you do with this is up to you as the passenger.
All I can say is.... If a crew member asks you not to use your PV, and you chose to stealth vape and are caught, after having verbal confirmation that it is not allowed... you are knowingly not following your crews instruction which can make for a really bad delay for yourself. I have personally seen arguments between passengers and crew members regarding PV's to escalate to obscene levels of stupidity.
This day in age with air travel being the way it is, it is very rare for a passenger to win in a confrontation with a flight attendant/pilot. Unfortunatelly, some cabin crew abuse this authority, and I apologise on their behalf. If you choose to ask, follow their instruction... if you are going to vape anyway, why bother asking in the first place. At least if caught, you can plead ignorance.
I vape regularly on flights, as a crew member, and as a passenger. Be discreet, not obnoxious.... dont blow smoke rings in the cabin just because "you can" (Yup, I have seen it happen)
Also, please.... if you are going to vape in the air, dont vape any device higher than 3.7V due to the recent instability of higher voltage devices. All it will take is one incidence of batteries venting inflight, and we are all done for! (Our privilege to vape that is)
See you in the air!
Safe Travels,
RIAFlight25