While it may sound silly, owl decoys hanging from tree branches or the sides of a chicken run can help deter hawks.
Amazon has a great range of owl decoys. From fake owl scarecrows to holographic hanging owl shapes that reflect the sunlight. Our favorite is the fake owl with moving wings, which would certainly seem realistic from up in the air.
The reason such decoys are effective is that by their natural behavior, owls and hawks are enemies. So if a hawk thinks there is an owl close by they are likely to look for an easier meal other than your chickens.