And BTW, a kettle is generally attributed to Hawks when in flight, usually during migration. But rarely for Red Tails as they do not tend to congregate for migration. Either way kettle is used for all hawks not directly to Red Tails.
And BTW, a short and simple web search yielded this:
A group of hawks is commonly referred to as a kettle, boil, or cast. These terms have been used since the Late Middle Ages and still have a place in society to this day.3 Hawks form large flocks during migration, taking advantage of rising thermal air currents. These swirling, circling flocks are called kettles.2 A cast of hawks is used to describe a group of hawks that are in flight, usually in a V-formation.4 Other terms used to denote a group of hawks include pot, an air pocket, and wake.
I guess there are not one, but SIX different names, used since the MIDDLE AGES for a group of hawks.