The NG video is very compelling.
For a few more actual real-life incidences, here are two documents to check out:
The National Transportation Safety Board's Safety Recommendation A-90-78 available online at http://www.ntsb.gov/recs/letters/1990/a90_78_79.pdf
"On January 20, 1990, an American Airlines DC-10 encountered turbulence near San Juan, Puerto Rico. The seat belt sign was on. Preliminary investigation revealed that an unrestrained 7-week-old infant sustained serious head injuries and was hospitalized with a fractured occipital bone, subdural hemorrage, and intra-cranial bleeding. The infant was the only occupant who sustained serious injuries."
The document is worth a read. I quoted the above specifically as it deals with a child severely injured due to in-flight turbulence alone. Most of the other case studies deal with survivable emergency and crash landings; details are provided of lap-infant fatalities in cases where the mother survived. In the summary of the document, the NTSB recommends that "[the FAA] require that all occupants be restrained during takeoff, landing, and turbulent conditions, and that all infants and small children below the weight of 40 pounds and under the height of 40 inches be restrained in an approved child restraint system appropriate to their height and weight."
The AAP gives some statistics in this linked publication, and summarizes with the following:
"A child on the lap of an adult cannot be effectively restrained in a motor vehicle or aircraft crash. … Hazards associated with the on-lap position are also well documented in aircraft crash investigations. Three children on the laps of adults were fatally injured and others nonfatally injured in the 1987 crash in Denver, CO, the 1989 crash in Sioux City, IA, and the 1994 crash in Charlotte, NC which were all caused by turbulence. The NTSB has reported 2 crashes in which CSSs were used and provided protection to children."http://aappolicy.aappublications.org...s%3b108/5/1218
The FAA, AAP and the NTSB all agree that children belong in child-specific restraints on airplanes.[/quote]