If Red-Tail - Yes as was said, and there are various morphs. I've seen a very white Red-Tail. So white (only very faint brown streaks here and there) that first impression was of a small Snowy Owl. It eventually had a very pale orange-ish tail in the band where it should be rusty. I think in a grown one you would see the demarcation where the color bands would be, but juveniles likely hard to see.
If something else - could be a Northern Harrier, likes to fly low over open fields, hunts mice. Slender wings. Very plain above (variations in color, but it's generally plain), white below. Look for wing wrist markings sometimes visible, and a white rump is definite.
Could it be a young Cooper's? It has no horizontal bands on the tail?