How to add a child to a flight booking?

[INXS]

Is it possible to do online? I already have my tickets (booked online, as always) but may need to add DC to my trip.

Can this be done online or do you have to call the airline?

Depends on the airline.

So there are some that will allow you to book (what looks like) an unattended 4 year old on a flight?
Or there are some that won't allow you to add children?
I have booked with Ryanair but my partner may be traveling with BA or one of a few other airlines, so I'm just looking for general advice at that stage

You can use the on-line chat option with Ryanair. They are usually very helpful.

My brother added my 11-year-old nephew to a flight he was on - he had to ring up as flybe don't allow an 'unaccompanied' child. He had a separate booking reference and i believe that meant the seat was elsewhere on the plane though.

Thank you all!

I've done this a few times and you have to book the ticket (some like BA force you to book an adult ticket) then you call them and they link your reservation numbers andxhanfe the reference to a child. I then received a refund for the lower price due to the air tax being reduced. Sounds complicated but it was quite simple.

Thank you ParisNext! That makes sense