In this video, you can see a chemtrail being sprayed for the whole duration of the video by an Aerlingus plane.
According to the contrails Wikipedia page that sources a PDF from faa.gov the altitude is a factor that effects contrail formation.
You can see that this plane rises in altitude although that does not seem to affect what is coming out behind it, therefore that is not a contrail.
You can see a Norwegian Airlines fly close to where the Aerlingus' trails are but it does not leave any.