I purchased a pair of round-trip tickets for myself and a friend. My friend will be using the outbound leg with me, but changes in circumstances means he's going to take a flight to a different destination rather than use his return ticket. Even if he could get a voucher for the unused portion of his flight, the total cost of the ticket is about what the change fee is.

Rather than let it go completely to waste, can we use the ticket to keep the seat next to me open? If I get the upgrade to first, then we'll just have him not check in and it'll be a gate upgrade for someone. If I'm stuck back in coach, I'm thinking he can check in, but not take the flight.

Would I turn both boarding passes over to the GA, or just tell them he isn't going to make it so they don't do the repetitive "last and final call for...."?

Would this work in general? Is it a bad idea?