("Jim" wrote)
I remember seeing balloons on two separate occasions and hearing a balloon
report to Center on one other occasion. The last was a report from
commercial traffic inbound to ORD reporting the balloons up around
12,000ft. Center nonchalantly acknowledged and the pilot clarified: "No, I
don't mean these are just some little party balloons, these are BIG, like
from a mall grand opening or a car lot!" This brought an immediate
broadcast advisory from Center about the location and altitude.


http://www.clusterballoon.org/
Fun site


Montblack