Scaling down dynamically created objects

I have a 2D game in which Aircraft and Missiles are instantiated at run time from prefabs.
However when the game is resized(scaled down) although the background and other objects scale down the dynamically created objects dont scale down and look really out sized.

What is the best way to scale down such objects(dynamically created)

Is there a way to detect screen resizing?

You can use the Screen.height and Screen.width properties to detect the screen size in Update().

If the user resizes, you can write a simple method to scale your objects proportionate to how the width and height of the screen have been resized.