It's supposed that Air France 447 crashed into the Atlantic because the pilots stalled the airplane when the frozen pitot tubes forced them to handfly it while cruising through the thunderstorm. But how could the pitot tubes freeze in that high altitude where the temperature was way below the freezing point? Isn't it that ice only forms on the aircraft between slightly above 0 and below -20 Celsius degree?
Edit) Wikipedia: "Below −20 °C (−4 °F), icing is rare because clouds at these temperatures usually consist of ice particles rather than supercooled water droplets. Below −48 °C (−54.4 °F), supercooled water cannot exist, therefore icing is impossible."