Are we talking 'MASS' or 'WEIGHT'??
The mass of the total body will never change whether it is in flight or in space, but the weight will??
In this case, the 'weight' (because of 'G') of the helo displaces that same amount of air downward and exerts a force on the scales. Hence no 'weight' change in readout.
If the air could escape thru cracks in the box, then the 'weight' would indicate less.
The mass never changes.