Just to repeat myself as it seems to have been missed.
Airports and aircraft are not public spaces.
While there is an assumption that in public spaces you may be photographed by anyone, I would think most people, while in a public space, would find it uncomfortable if a stranger where to stop, take a few photos of them, and then walk off again.
Translate that situation to an airport or an aircraft, which are areas of restricted access and more akin too or actual private property, where the stranger with the camera might be thinking it is only a few photos, but for the person at the other end of the lens it might be stranger number 5, 10 or 25 that day pointing a camera in their direction.
On a number of occasions I have noticed people standing with their cameras appearing to take photos while I was doing my walkaround. I have then gone and got my own camera and if they were still there when I got outside again I have pretended to take pictures of them. On each occasion they disappeared almost immediately. They certainly didn't like being photographed, so what made them think I did?