Family Tachinidae
Alabama
Note about this photo from Patrick Coin, a North Carolina naturalist:

"I believe you've captured two flies in flight, presumably a male and a female.
Looks like the one above is doing the flapping, and the fly below (female?) is keeping its wings still.
The whitish appendages are scales that cover the halteres (vestigial wings).
Seems like lots of tachinids have them."