In the early eighties Northern Europe had a particularly cold spell.
Zurich was virtually closed and Swissair's fleet was grounded for a couple of days.
Zurich Kloten is situated in a mountainous bowl which often retains the katabatic air. When a front passes over in winter there is often a sudden but often temporary period of freezing rain.
I think on this occasion two fronts passed over before the freezing air was displaced.
It was impossible to walk or drive - although in the windless conditions it was possible to maneuver an aircraft but not to push it back.
The main operator that flew into ZRH during this time was BA who did not have the braking coefficient restrictions of Swissair.
It is interesting to note that they were also allowed to operate for 11hrs across the Ogin after an engine failure and fly 777s in colder air than other operators.- but that it is straying off the subject.
Some of you might remember the 747 that broke up in anchorage - although the runway had reasonable braking action the taxiway didn't.
The crew gave up trying to move the aircraft in strong cross winds and shut the engines down.
The wind then took over, weather cocked the jumbo and blew it down the embankment.
Think everyone had a lucky escape.