There are actually some really good times where you should turn airplane mode on, outside of flying! :-) With my iphone I turn mine on fairly often. For example if you want no messages and no phone calls, but still want your iphone on for wifi or other things like flying a drone! Which I do :) This way when flying the drone you aren't interrupted by someone messaging you! Airplane mode prevents this.
If I was traveling ot another country I would probably use it also since I wouldnt want international phone calls (expensive).