I'm with those that think babies should not be allowed to fly unrestrained. But the facts are that, at least in N.America, we're too cheap to pay for a seat for the baby, thus we have all those "infants in arms". There's no way to effectively restrain them, whether in the arms or on the floor. They should be strapped into something safe.
But it won't happen till a planeload of babies comes to grief.