The jetstream, like all weather and winds, is on a continuum. There is no barrier where outside of the jetstream the air is static. See the principles of flight

The jetstream, like all weather and winds, is on a continuum. There is no barrier where outside of the jetstream the air is static. See the principles of flight and how air functions VERY close to a wing for an example. This is actually a good example, though a bit unrelated. https://news.ycombinator.com/item?id=13829625 https://news.ycombinator.com/item?id=13829625