The first occurrence of chemtrails was observed in the US, but that is not to say that they were not occurring elsewhere. Presently, Chemtrail spraying has spread all over the globe, with reports of sightings coming in from every corner of the Earth.
Areas covered by chemtrail spraying have increased and it would seem that the frequency of chemtrail spraying is on the rise. With new eye-witness accounts of excessive chemtrail diffusion being reported by pilots virtually daily. As well, new reports are being documented of strong metallic smells being noticed in areas where chemtrail spraying occurs in the US.
In fact, spraying has become so frequent, that it is accounted for in weather reports so as to not arouse suspicion. That is not to say that random spraying does not happen besides the charted occurrences.
Although there are numerous types of chemtrails, it would appear that the vast majority of chemtrail-monitors would agree that the primary and most frequent types of chemtrails are for the purposes of altering weather.