[amsat-bb] Near Space Flight Question

Pardon me asking this question as it only relates to amateur satellites in a small way as the packages I refer to don't achieve escape velocity.

Over the years I've followed the work being done regarding flying radio packages on balloons.

I'm familiar with the scenario of a balloon carrying a package that will go to a predetermined altitude, bursting then returning to the ground.

With the advent of the round-the-world experiments with small party balloons, how do project organizers keep such equipment in the jet stream so that they travel long distances without the equipment going so high that the balloon bursts?

Dave Marthouse N2AAM dmarthouse@gmail.com