I get a few dirty looks. I wonder if they are directed at my mothering or at my child. Zachary's crying brings up issues for the other passengers. I sincerely believe people are jealous that they can not express their feelings in the same way. A baby that cries can be frustrating to parents.
Parents tend to have to deal with a lot of pressure including societal judgement when a child cries.
Sheila Kitzinger has a book out called The Crying Baby . It not only talks about reasons a baby might cry, but it talks about the emotions of the parents and ways for them to vent frustration. The book deals with the fact that it may be harder to deal with babies who cry and that the emotions that crying bring up are important to deal with as parents - especially mothers or fathers who stay home all day. Also issues or conflict, external or internal, experienced by parents affect the child. By dealing with or solving these emotional issues, the crying might be alleviated.