Yikes! 
"In Missouri, people tend to notice ballooning spiders most in the spring and fall, though ballooning may take place any time of the year for some species.
How far can spiders expect to travel on their gossamer aircraft? Because spiderlings are so small and difficult to see against a background of white sky, it is impossible to come up with species-by-species accounts and averages. One spiderling may land just a few yards from its take-off point, while its sibling may travel 100 yards. Still other species may go for miles and perish in a lake, or wrap themselves around the neck of an unsuspecting angler.
Charles Darwin observed the arrival of ballooning spiders on board a ship 60 miles from the coast of South America. Arachnologists-people who study spiders-have concluded that most ballooning spiders reach heights of 200 feet or less, though people have seen spiders at 5,000 feet and a few at 10,000."
Yikes!