What's the wind velocity in a 747's wingtip vortex, & how long can it stay above 40 mph? This has a rather unusual objective. A number of years back, I wrote a sort of science fiction short story about a team of wing-suited skydiver/base jumpers who sneak into an international airport to run into the wake of a departing 747 to soar in the upswing sections of its wingtip vortices. Not the kinds of jumpers you'd want to bring home to mama. I've read that wtv's of a departing commercial jet can reach velocities of over 100mph. I assume that to be an initial peak velocity, & that it drops off quickly, but I'm not sure what velocity it lasts the longest at. It has been claimed that wake turbulence from commercial jets remains dangerous to small private a/c up to 10 minutes, but the velocities are never specified. I have little-if any-doubt that the initial swirl of a 747's vortex can violently toss a wingsuiter into the air. But how long can the diminishing winds sustain him?