You can see the curvature of the Earth from the typical jump height of 13,500ft, but it's nowhere NEAR as pronounced as that. The curvature you're seeing is definitely the result of using the wide angle lens, probably around 10-17mm in 35mm format.
What you actually see is just the slightest curve, but it's noticeable.
Mark Davis
Palm Beach Gardens, FL
amateur photographer, hot rodder, motorcyclist, adventurer
"Four wheels move the body. Two wheels move the soul."