Interestingly airlines already do this. When airlines ask for volunteers to take the next flight, it could due to a range of factors but last-minute business travel is one. They will absolutely sell a last-minute ticket for $2,000 to a business traveler when the flight is already overbooked, then offer someone $1,000 to take another flight. Usually everyone is satisfied and the airline profits.

If it were the US they could just seize the cheap ticket and resell it for more per https://en.wikipedia.org/wiki/Kelo_v._City_of_New_London.

I’m assuming this is a joke, but if not - that’s not how Kelo worked. Kelo is bad law, and a horrible court decision, but it doesn’t mean any private company can just take your stuff…

Considering the carbon footprint of air travel, empty seats is decidedly not what we should want.

Airlines keep seats to sell at the last moment now.

I thought they famously did the opposite of this by overbooking flights

Both happen. Keeping seats happens more often in Europe.

I flew Munich-Oslo yesterday. Look at the prices for that route for later today, for next week and for next month. The seats are the same on most of the aircraft, the available business class you see is just regular seats being kept free for expensive tickets. And when the search engine says "4 seats are left at this price", that means that the airline is keeping some to sell at higher prices.

That's relatively rarer in Europe compared to USA.

Don't know for all europe, but air france overbook all the flights Source: my father was working with the CEO.

Which sometimes causes that you are upgraded for free. ;)