Have seen this term somewhere but can't remember where and can't find any info. Is there such a thing or am I imagining it?
Let me down gently.....
I deny that there is any such thing as a "
Jet Standard Atmosphere". Google seems to confirm it.
There is generally only one standard atmosphere, the US 1976 Standard Atmosphere. The ICAO and ISO Standard Atmospheres just extend this model to higher altitudes.