[voisin]

Unfortunately this is not correct. It isn’t legally theft (though morally it surely isn’t the right thing to do). Theft implies someone was “manifesting the desire to exclude others” and someone else took it anyways. Once you hand over your luggage, you have a contract with the airline whereby you’ve waived many of your rights and limited the few that remain. Once the luggage goes missing, you are entitled only to those limited rights under your contract with the airline. The newly found luggage can be sold as unowned goods.

There’s centuries of common law that back this up. It sucks, yes.

[guenthert]

> Theft implies someone was “manifesting the desire to exclude others”.

That can't be the whole story though. You can't keep stolen property, even if you bought it from a 3rd party and were under the impression that the transaction was legal. Lost&found might not be stolen, but if the airline 'finds it' without the intention to return it, it's not that far off.