A Seattle air traffic controller spotted a heavily loaded 747 crossing paths with an Air Canada jet just moments before the Canadian aircraft was thrown out of control at 35,000 feet, injuring 10 passengers.

According to sources close to the investigation, the Seattle controller ordered one of the planes to change altitude after noticing that the 747 was crossing paths with Air Canada Flight 190, an Airbus A319 en route from Victoria to Toronto last Thursday morning carrying 83 passengers and five crew members.
Moments after the controller issued his order, the Air Canada jet was pitched into a series of rolls and dives that threw passengers around the cabin and caused undetermined damage to the airplane, which diverted to Calgary for an emergency landing.
Although the investigators have so far refused to elaborate, sources close to the investigation say the Seattle controller spotted the potential for a turbulence encounter between the two jets after noting that weather conditions were nearly ideal for the creation of mountain waves, invisible aerial currents that form downwind of hills or mountains.
Because they contain wide bands of rising and falling air, mountain waves can make it difficult to predict how quickly wake turbulence behind an aircraft will dissipate. The incident took place in Washington airspace about 120 kilometres south of Cranbrook, B.C., an area noted for wave activity. It is popular with glider pilots, who ride the rising parts of waves to altitudes of 25,000 feet or more.