I was watching an Air crash investigation video where the cause of the plane crash was determined to be due to blockage of fuel pipes by ice crystals (from the water in the jet fuel) which would have formed while the plane was cruising over Siberia where temperatures are as low as −74 °C. Now the engines were working fine until the fuel temp. was −30 °C. But as soon as it started getting warmer near London, Heathrow and the fuel temp hit −20 °C the ice crystals coalesced to form a mesh that completely blocked the fuel pipes and caused the engines to lose power and end up crashing.
My Question is: What caused the ice to not stick at a colder temp (−30 °C) when I believe the molecules would be vibrating slower than those at −20 °C? It seemed from the investigation's experiment that below −20 °C big ice crystals don't form at all, if they do they're tiny. So why does the increase in temperature help ice sticking?