There's no question that infants who are actually on the plane are safer in a dedicated seat with virtually any type of infant seat. However, you are probably right that such a rule would cause some parents to drive rather than fly.

I'm not certain that flying is safer than driving. At least one source puts the auto death rate over a number of years at 1.3 per 100 million miles and the aircraft death rate at 1.9 per 100 million miles, and this didn't include the massive death toll of 9-11, nor the massive number of deaths over the past 14 months. Here is the link: http://www.pbs.org/wgbh/nova/space/h...is-flying.html

But the fact is that the risk of dying in either a car or airplane accident is so small that it really is not worthy of consideration. What is worth considering is whether or not an infant in arms is likely to be disruptive and make other passengers on the plane miserable.

Currently, there are no safeguards to prevent parents from claiming 3- and 4-year-old children as infants and taken as lap children. I have seen children who could not possibly be under 2 traveling as lap babies, and these kids have been highly disruptive. Also, there is just no way for a single person traveling alone with a huge kid in their arms not to infringe on the space of their neighbors. Perhaps two adults traveling together could handle a lap baby in such a way as to not disturb others, but one can't.

In addition, infants like to be held, but they also like to sit without being touched, and tend to scream and cry when overheld. This ruins everyone else's flight, and could easily be avoided by requiring all passengers to have their own seat, or be able to use a bassinet on the bulkhead.