I would say that the system is still open. Now if the top of the scale were an air-tight container inside of which the helicopter did its hovering, then I wold assume that the weigtht would be the same as if it where landed.

For the parakeets, tie the feet of nearly 100 to the top of the plain, feed then uppers and let them help the plane fly. If they are not burned out and die from overwork, then you may have 200 at the destination.

If you do this type of scenario, would they actually cancel the weight of the parakeets inside? If so, the you could have 200 in the plane and 100 helping to give lift to the plane!