What about when you can't select seats?
On a separate but associated note, how can I book seats together when my ticket has been booked by a travel agent in association with a cruise? I can access the booking to add passport information, contact details etc but I can't see baggage allowance, reserve seats or upgrade. Flights are with BA.
In this case I will be mightily p***ed off if I get to the 24 hour checkin window and we don't have the option of seats together.