I don't see a lot of big white bugs that fly. Could it possibly have been pale yellow with black striping? In that case it might be a cicada killer wasp. They don't seem to mind flying around humans or flying low to the ground when humans are around, but they won't hurt you.

Since you said you were mowing tonight, it could be some sort of moth that comes out at night? Maybe something like the white lined sphinx?

There's so many thousands of insects around and I doubt any of us have seen more than a small percentage of the ones found in our areas. You might try the website bugguide.net. You can click on a line drawing at the left that most resembles the shape of what you saw, and see where that takes you. It might take you to a page that has what you saw somewhere on it.

On the linked webpage, there are images of insects commonly found in OK. Maybe you'll see a photo of it there.

Insect Identification--Insects of Oklahoma

Well after my husband came home and I described the insect to him, he suggested it was probably a ground hornet. So, I go online and looking for black and white hornet and sure enough I found a similar picture. Seriously?! Hornets!?!? Ugh! lol

I'm glad you figured it out. We do not often see ground hornets here, and I'm glad, but we have tons of yellow jackets, mud daubers and red wasps.