Infants shouldn't allowed on to any means of transport apart from their parent's car. Also, what kind of dick takes their weans to things like concerts, the cinema etc. then have to leave half way through because it wont stop crying? Fucking idiots.
I was talking about months due to a horrible experience yesterday old but your probably right with 4 as the limit.
I was flying out to the states a few years ago and was stuck in front of a family with 2 young kids screaming and crying the entire flight. As I looked round the parents were both watching the TVs with their headphones in. The flight attendant came down at 1 stage and asked the mother if she could try calming one of them down and took him into her arms for a walk down the plane. I was sat beside some old doll and she turned and said something to the Da. Being the nice guy that he was he punched the back of her chair and told her to mind her own business before someone stepped in and told him to relax. Some people are just oblivious, others are just ****s.