Makes me remember an incident at IAH waiting to board a flight to Mexico a few years ago.

A woman and her young daughter were not permitted to board the flight without a notarized letter giving permission from the father.

It seems that CO agents at EWR had neglected to advise the passengers at check-in of the requirement (Where the father was available to provide the document)

It was a very nasty scene, not handled well by the IAH gate staff. I had a lot of sympathy for this poor woman and child.