The very existance of the northern and southern jet streams was unknown until the Second World War. Exploiting them to speed up journey times is an even more recent trend.
Being extremely picky, actually just before. The first paper explaining the existence of the NPJ was published in 1940.
Here it is
Gann, in his book "Fate is the Hunter" talks about the first exploratory use of jetstreams by air transport pilots during WW2.
The possibility that some modification is caused by aircraft flying in those regions is certainly there. I suspect more due to high tropospheric / low stratospheric emissions, rather than direct movement of air, but I may be wrong in that regard and I don't think that anybody has looked hard at the question.
In the case of our research however, we're *not* thinking much about the impact of aircraft operations on climate change - other people are doing that. We're thinking about the impact of climate change on aircraft operations: a linked, but somewhat different question.
G