I just got back from a trip, and I vaped in the lavatory on the planes without problems. Also, during a layover in Denver, I asked a security person where the smoking area was. When she told me how far it was, I asked if that was the only place I could vape. She stated that vaping is legal anywhere in the airport, but that if someone complained, it can develop into a sticky situation. Toilet stalls can be your friend.