Written by: Stan Lee
Drawn by: Jack Kirby
Inking: Dick Ayers
Lettering: Art Simek
I think it's clear where the inspiration for this image comes from: Glaucomys sabrinus, the North American flying squirrel. Although the dialogue mentions Reed's body being a parachute, I much prefer him using his body to create a glider effect, as seen.
It's not an image or usage we've seen in the 50 issues since, sadly.
Check out our coverage of Fantastic Four #18 on our seventeenth episode: No Funny Title Springs To Mind
[audio http://traffic.libsyn.com/ffcast/Episode_17.mp3]