There's currently no ban against packing e-cigarettes in your checked baggage before a flight, but the FAA seems to be convinced it's a pretty terrible idea. The FAA has sent out an alert to airline operators asking that they remind travelers that exclusively transporting e-cigs in a carry-on bag is a safer way to go for everyone involved.
Pointing to recent incidents — one plane had to be evacuated last summer when a checked e-cigarette overheated and caused a fire — the FAA notes that it's much easier to spot potential hazards if e-cigs are in the cabin and visible to flight crew and passengers alike. And if you're one for modding the components inside, you might be raising the odds of a problem in the skies. "The danger may be increased when users modify and rebuild their reusable e-cigarette devices and interchange original and aftermarket batteries, heating elements, and vaporizing components," the FAA said.
"E-cigarettes have overheated or caught fire when the heating element was accidentally activated."
So again, airlines aren't being required to ban e-cigarettes, but the FAA is giving them a nudge to play it safe and urge passengers to exclusively make them a carry-on item. Just don't go smoking them at 39,000 feet; most major airlines do have hard restrictions in place against that sort of thing.