....... is passenger does not show up for their flight and does not inform the airline in advance.

…………………. is used to describe a passenger who shows up at the airport to board their flight without prior confirmation or ticketing changes.

If you don't travel on the outbound flight and fail to reconfirm for the return flight, the return ticket may be marked as ………………….., and it could be canceled."

if you're flying on ………………..…, you need to wait until all passengers who have confirmed tickets are boarded. If there are remaining empty seats, you might be allowed to board.