The airsickness plague replaced its ancestor plent airsickness. It has become much more deadly causing its host to first have flu-like symptoms. Then after a week or so their internal organs start to hemorrhage and fail causing them to die. Like its ancestor it only effects plents, however due to many other species depending upon the plents as food they also died as well once all the plents were gone. In addition after all the hosts were gone it too became extinct. The following species because extinct; cloud swarmer, duke yuuvee, parasite phlyer, zeploon cloudswarmer, maternal hiveballoon, bleeding bellyoon, air cretin, cloudeater, aeroswarmer, tropsnapper, dusksnapper, stratovermes microplaque, stratovermes guttoplaque, plentivitis, dirtsident and greeny nimbuscloud.
The reason why they have not spread to the biomes below is because after being so specialized for atmospheric life it becomes "crushed" as it gets lower in the atmosphere. Thus all microbes that make it to the surface quickly die from the increased atmospheric pressure.