All you who are equipped with the brilliant Red Baron NZ mesh, you are in for a treat!
Take yourself to Mount Cook airport (NZMC), and start up a flight in an aircraft with ski gear. (Seems to work with tricycle and float gear planes too, but is rather unrealistic).
Take off, and climb over westwards the peaks and head towards the Tasman coast. Once you reach the sea line, follow it north until you see the Fox Glacier and Franz Josef Glacier on your left hand window.
Make sure you are high enough that your altitude is about the same as the top of the glaciers, then head for the tops of the ice slopes and carefully land on the snow. (Make sure your 'crash detection' setting is turned off in the realism settings)
Once you touch down on the slope, you will begin sliding backwards, so cut the engine, and use your brakes and rudder to get you facing down the slope rather than up at the sky. You will begin to slide faster and faster, and now all you have to do is try and remain in control! As you hit bumps in your path, you will be shot off into the air, so finish you flight by gliding off out the mountains, and restarting your engines
Try and see how fast you can go (Shift+Z brings your speed to the top of the screen) before you become airborne again. I managed 105kias today
Other fun glacier activates include trying to make a full stop landing on the sloped glacier, or sliding a chopper down the ice...