There is netting that comes in large sizes for pheasant aviaries. Netting is usually sufficient to keep hawks out. You can use poles to support it across the span.
A good rooster with each flock has kept hawks from taking any of my hens.
When one thinks they don't have predators looking for a free chicken dinner, they need to think again. Hawks, raccoons, opossums, foxes, coyotes, weasels, dogs and feral cats are virtually everywhere.
I have no idea how much one would cost but could a parachute from a supply store work?