is it safe

I have taken pictures out the plane window before they had digital cameras. They didn't seem to care at all. Once you get on the plane just ask the stewardess / attendant. If there is a problem with it they will let you know and if there isn't a problem with it they will let you know when it is safe to bring your camera out so you can start snapping pictures. I don't think there would be unless you have a massive camera you have to sit on a tripod in the middle of the aisle with a huge lens to get the pictures :) That might cause a problem :)

Well I can't think of any reason why it would be dangerous. I have never been on a plane before though, so I don't really know.