In his book, Sled Driver, SR-71 Blackbird pilot Brian Shul writes:
I'll always remember a certain radio exchange that occurred one day as Walt (my back-seater) and I were screaming across Southern California 13 miles high. We were monitoring various radio transmissions from other aircraft as we entered Los Angeles airspace. Though they didn't really control us, they did monitor our movement across their scope. I heard a Cessna ask for a readout of its ground speed.
"90 knots" Center replied. Moments later, a Twin Beech required the same.
"120 knots," Center answered. We weren't the only ones proud of our ground speed that day as almost instantly an F-18 smugly transmitted, "Ah, Center, Dusty 52 requests ground speed readout."