I take photos on planes, in lounges, in restaurants.
I am discrete. I do not use flash. I don't linger awkwardly with the camera out. It's a small camera, I pull it out and snap the photo and put it away. And do it as naturally and to blend in to the movements and actions of a normal passenger or diner.
When I was at El Bulli it was fascinating, more than half of the tables were taking photos with flash. You could tell this was a new experience for them, I took photos but discretely as I saw flashes going off across the restaurant. Really quite amusing.