SR-71 Blackbird pilot Brian Shul reported one exchange. His SR-71 was screaming across Southern California, 13 miles high and its crew were monitoring cockpit chatter as they entered Los Angeles airspace. Though they didn't really control the SR-71, LA monitored its movement across their scope. The SR-71 crew heard a Cessna ask for a readout of groundspeed.
"90 knots" Center replied.
Moments later, a Twin Beech required the same.
"120 knots," Center answered.
An F-18 smugly transmitted, "Ah, Center, Dusty 52 requests groundspeed readout."
Center (after a slight pause): "525 knots on the ground, Dusty".
The SR-71 realised how ripe a situation this was for one-upmanship: "Center, Aspen 20, you got a groundspeed readout for us?"
Center (after a longer than normal pause): "Aspen, I show 1,742 knots"
No further groundspeed inquiries were heard on that frequency.