would employing commonsense made a difference?

Air Canada passengers hurt in turbulence

"It happened very fast," one unidentified female passenger told the media at the airport. "One side of the plane just went up a little bit sideways and then just went back down. Our friend was really hurt. ... She flew up and hit the ceiling and went back down."

hmmm... seems to me that even if the "seat belt fasten" sign is off, it is a good idea to keep it buckled. air currents do not necessarily announce when they will become turbulent.

just because you can sit in an airplane without a restraint fastened doesn't mean you should.