http://news.bbc.co.uk/2/hi/americas/8085539.stm
These paragraphs struck me as very unusual. Maybe this is a common occurrence for jets taking off over oceans with storms, but I've never heard of this.
"Meteorologists say that the Air France Flight 447 had entered an unusual storm with 100mph (160km/h) updrafts that sucked water up from the ocean.
As the moisture reached the plane's high altitude it quickly froze in -40C temperatures. The updrafts would also have created dangerous turbulence, they say."