Stalling at high altitude

You should turn pitot deicing on: certainly some (all?) aircraft will have their airspeed indicators fail as they ice up otherwise.This affects the instruments but I wouldn't think has anything to do with stalling.Other aircraft also have deicing for (variously) wings, engines and propellors.As I understand it, the risk of real icing is highest when climbing or descending through cloud rather than just cruising at high altitude through clear, dry air.Obviously icing of wings and power plants would make a plane unable to maintain height & speed.However, I also understand that Flight Simulator does NOT model icing, other than of the pitot. So that would be irrelevant, even if there are switches for deicing. Anyone know different?Two things that are relevant are that:a) The higher you go, the lower rate of climb you should employ. Typically, the autopilot will climb an FS jet airliner at 1800 feet per minute immediately after the take-off phase. As you get higher, you need to reduce this progressively to maybe 800 fpm, or whatever is required to keep the speed up and the nose at a sensible attitude.:( There are 2 measurements of airspeed: indicated and true. There is a toggle on the "Realism" tab of the menu to switch which your instruments show. Somebody was trying to explain the technicalities, but basically as the air thins at altitude, the aircraft can fly through it faster - so at altitude, true airspeed and therefore the speed over the ground could be of the order of 500 knots. The GPS usually shows groundspeed somewhere.However, because the air is less dense at height, indicated airspeed (traditionally measured by amount of air flowing through the pitot tube) is less - as is the ability of the thin air to provide lift from the wings. So indicated airspeed might be c. 300 knots.It doesn't really matter which you use as long as you understand the implications for stalling speed: using indicated airspeed you might stall at 150 knots at high altitude - which is similar to what you see near the ground - but using true airspeed you might stall at 250 knots, which is much different to what you see near the ground.You don't say how high is high, as it were. Flight Simulator isn't 100% accurate, but www.airliners.net is a useful place for some relevant data: e.g it gives max cruising speed for the Airbus A330 as being 475 knots (true!!!) at 33,000 feet.Going back to www.airliners.net, I'm finding that some 3rd part aircraft I've downloaded throw up odd results in Payload and Fuel settings. e.g. the Posky A330 shows as being just over max weight with 100% fuel but no payload at all! Airliners.net typically gives a much lower empty weight than is in the aircraft.cfg file.I think there has been a change between FS2002 and FS9 in the way empty weights, fuel and payload are handled.However, whether the calculated weight has any bearing on the way the aircraft flies in FS9, I can't say. I would presume it does.