That's taken from a book called "Sled Driver" by Brian Shul.
If you happen to have a copy they change hands for silly money.
"In another famous SR-71 story, Los Angeles Center reported receiving a request for clearance to FL 60 (60,000ft). The incredulous controller, with some disdain in his voice, asked, "How do you plan to get up to 60,000 feet? The pilot (obviously a sled driver), responded, "We don’t plan to go up to it, we plan to go down to it." He was cleared."