For all those thinking the federal ban on "smoking" tobacco on commercial flights doesn't apply to electronic cigarettes, here's your unequivocal answer from the Department of Transportation: Nope. The DOT on Wednesday officially banned vaping "in all forms, including but not limited to electronic cigars, pipes, and devices designed to look like everyday products such as pens" on all planes entering, exiting, and flying around the US. The announcement expands on a statement previously issued by the department that it had considered to be "sufficiently broad to include the use of electronic cigarettes" but that NPR reports was seen by some to have a loophole: It did not explicitly define "smoking," and e-cigarettes release vapor, not smoke.
Ars Technica notes that no US-based carrier had explicitly allowed the onboard use of e-cigarettes. But the DOT's lack of a crystal-clear ruling led to things like the FAQ on the website for blu eCigs, which asks, "Can you vape on a plane?" and answers, "It depends"; it notes the DOT hadn't issued an official ban and instructed fliers to check with individual airlines or ask their flight attendant. In its now-official ban, the DOT specifically calls out the "number of harmful chemicals" that studies indicate are in aerosol fumes, and it notes that while further research is required to "fully understand the risks," it will take a "precautionary approach" in the meantime. Passengers are already barred from both transporting battery-powered portable electronic smoking devices in their checked bags and charging them on board aircraft. (Vaping is apparently still allowed here.)