Funny how the word emergency comes up in the Vancouver Sun!
The Aviation Herald account uses no such word - typical anti-AC bias IMHO.
CC
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Incident: Air Canada B763 near Vancouver on Aug 21st 2010, whistling sound from windshield
By Simon Hradecky, created Saturday, Aug 21st 2010 21:55Z, last updated Saturday, Aug 21st 2010 22:03Z
An Air Canada Boeing 767-300, registration C-GHLV performing flight AC-25 from Vancouver,BC (Canada) to Shanghai (China) with 166 passengers and 9 crew, had already reached FL300 110nm northnorthwest of Vancouver about 20 minutes into the flight, when the crew decided to return to Vancouver. The airplane entered a holding at 14000 feet for about 20 minutes, the crew indicated they would prefer to not perform a visual approach. The airplane landed safely on runway 08R about one hour after departure.
Air Canada reported, that the crew noticed a whistling sound from the windshield and decided to return as a precaution.
A replacement aircraft is expected to perform the flight, the arrival in Shanghai is currently estimated with a delay of 13.5 hours.
http://flightaware.com/live/flight/ACA25/history/20100821/1822Z/CYVR/ZSPD