an a parent travel out of the U.S.with a 3yr old child without other parents permission

If the parents are still married, then such travel, without permission, can be a felony abduction. If the parents are divorced, it depends on the language of the custody orders. In either event, the traveling parents needs a permission letter from the other parent, whether traveling by air or other means (car, train).  You can Google: CA Penal Code §278.5.