NASA still uses the SR-71 out of Edwards.
Or at least, they did until recently.
A friend of mine used to be a Flight Engineer on the SR-71 with NASA. She is the woman with the most supersonic time in world. Pretty cool distinction.
dd
Gotta like a fast woman!
My recollection is that the SR-71 max landing weight is pretty close to empty weight plus some fumes, and it flies right about in the coffin corner where stall speed meets transonic buffet.