Well, let’s do some rough math here, as we at the Stright Dope are so fond of. I believe the circumference of the Earth is something like 25000 miles. Divide that by 24 hours, and you get about a required average speed of just over 1000 MPH. since there are at least a couple of planes in the world that are capable of that kind of speed, with refueling and the like, even changing planes if the engine can’t last wouldn’t take too long. You’re friend is nuts.
A back of the synapse calculation shows that a bit over 1000 MPH should do the trick. Assuming that the logistical problems of refueling and airspace clearances can be taken care of.
The Blackbird tops out at over Mach 3, but doing a quick-n-dirty estimate, I’d say it would average no more than Mach 3 since it has to slow down to refuel. The hypersonic KC-135 hasn’t been completed yet. (Or conceived of yet.)
So let’s say the Blackbird has to go 25,000 miles above the earth’s surface (continuing the quick-n-dirty estimate thing). According to http://www.allstar.fiu.edu/aerojava/mach.htm , Mach 3 at 60,000 feet should be 2000 mph. So, in 24 hours, the Blackbird should travel 48,000 miles, a little less than twice around the world.
So, if you leave some wiggle room to do all the equations I didn’t do (a real average speed considering all the slow-downs for refueling, a real circumference at 80,000 feet, the real speed of sound at 80,000 feet) you’ll still have the Bird travelling around the world once at the very least.
Be sure you use a dual-control model. I wouldn’t want you falling asleep at the stick at Mach 3.
Any similarity in the above text to an English word or phrase is purely coincidental.