Before a passenger plane takes off, the flight attendants deliver information to everyone about oxygen masks, under-seat flotation devices (in the event of a water landing*), and the importance of remaining in one's seat with seat belt connected when the seat belt light is illuminated. This is because, regardless of pilot ability or the quality of the aircraft, unforeseen elements like air turbulence can toss the plane around without much warning.

A recent Qantas flight might be evidence for adding computer malfunction to the list of reasons to wear a seat belt on a plane.