Originally Posted by bandana1948

I did not slip up, as some commentators here have suggested.

All three passengers were clearly indicated at the time of booking. When I "view" the booking online, my child's name is indicated as a passenger with a seat assignment that says "In Adult's lap". Air Canada, the first carrier in this itinerary, has a record of my daughter in their system, but sees that no ticket has been issued to her.

United.com indicated on its website that the fares/fees etc. for ALL of the passengers would be indicated on the final page, just before I had to make payment.

I received a quote, and paid what it quoted. I had no reason to second guess United's quote, to contemplate even for a moment if it was a mistake, or feel the need to follow up with United.

My only experience traveling with my daughter has been on a domestic segment for which she did not need a ticket.

Some commentators seem to suggest it is my fault and not United's; that I ought to have known better; that it is not too late to fork out more money.

I respectfully disagree.