Unused Food Is Thrown In The Trash
You already know just how questionable airline food can be, so it should come as a relief to know that whatever is left over when the flight lands is thrown away. This isn’t the absolute rule, but is usually decided at the discretion of the captain.
While it might not be the best practice to waste leftover food, it is the reality of the airline industry. Most food on board can’t be given to shelters, either.