Let me add that after that accident some woolen threads were installed at the roots of the wings of the MD80, free to shake into the wind, in order to facilitate the identification of subtle icing Vetrone by the crew, often unnoticed.
Mostly correct
but they were not put there to depend on the wind for visualization. They required movement by a pole device held by a man on a ladder. If you couldn't move them they were probably covered by a film of ice.
The biggest problem with the dispatch with wing ice was the first flight of the day after an overnight in drizzle/snow. The snow would be blown off on the ground but they missed the check underneath for ice.
Contrary to popular belief there were only a few incidents of ice due to cold soaked fuel in above freezing conditions.