A plane barreling down a runway isn't likely to collide head on with anything. If it does, the passengers have more things to worry about than projectiles flying forward through the cabin. Though, I do tend to agree that infants be secured in an FAA approved carrier, buckled into their own airplane seat. Airlines would love this, as it allows them to collect revenue for the seat being occupied. Whether they would charge full price or not is a whole different thread topic.