Hi, wondered if anyone could help with information for the following. My cousin is currently in orlando and has a return ticket booked for Friday. He is strongly considering taking a transatlantic cruise back to the UK, so obviously won't need his return flight.

He is aware he won't get any money back for his flight, as it was a mpm booking. Does he need to let the airline know, or just not turn up? What is the best thing to do in this instance?