Clear Air Turbulence Remains a Travel Concern
Clear air turbulence shook Continental Flight 128 as it flew from Rio to Houston, causing the plane to make an emergency landing in Miami. Far less predictable than turbulence associated with storms, clear air turbulence injures around 58 US passengers per year.Those injured are usually not wearing seat belts when the clear air turbulence strikes.
Clear air turbulence is often referred to as "air pockets", and they usually occur around mountain ranges, or near the jet stream at high altitudes. There's actually a turbulence forecast, but your mileage may vary in terms of accuracy.
National Transportation Safety Board data indicates the instances of turbulence severe enough to cause passenger injuries has remained steady since 1990 at about eight per year, and efforts to reduce them haven't shown results, USA Today reported Tuesday.
During hot summer months, airline passengers tend to feel more bumps because of rising pockets of air, generated by the heating of the ground. Thunderstorms create extreme turbulence, which is why airline pilots are trained to steer well clear of them
I've encountered this phenomenon quite a few times, mainly while flying between Vancouver and Toronto and between Sydney and Auckland. It only lasts a few seconds but is very abrupt, but nothing as bad as described in albertacowpoke's story.
Also see the Civil Aviation Authority's info page.