wear seatbelts! it is even printed on the seatback in front of you.
pilots should be more alert for turbulence...many don't monitor the outside air temp (static air temp) for clues.
monitoring winds aloft constantly may help too. wonder what the forecasts/airmets/sigmets were for that day.
also...even though kansas is as flat as twiggy, mountain wave can be felt up to 700 miles downwind from the rockies.
just heard one passenger say that there were a few little bumps before the big one.