The Transportation Safety Board (TSB) continued its investigation of an incident in which passengers were thrown from their seats and objects hit the cabin ceiling during a harrowing few minutes that forced the Toronto-bound flight from Shanghai to stop in Calgary for medical help. ... Rod Hayward, an aviation expert at the University of the Fraser Valley, said sudden turbulence in clear skies can sometimes be caused when a plane flies through a jet stream, a kind of narrow, fast-moving current of air. That sudden increase in air velocity, sometimes reaching 100 knots, can cause aircraft to shake violently, he...