Feel free to be as pedantic about this as you want.
A friend wants to know
"If a lorry fully loaded with chickens weighs 5 tonnes. How much does it weigh if all the chickens start flying around in the back?"
The chickens are free and can fly as much as they want to. The lorry is hermetically sealed with sufficient oxygen so they don't die. Schrodinger is elsewhere at the time.
His basic question is that in order to fly there must be a downwards force and presumably this eventually acts on the floor, so the lorry still weighs the same. Apparently it's puzzled him for years.
Oh and feel free to change tonnes to Newtons.