Weird AI Problem?

Hello all!

I was playing around with the sim after installing some WOAI packages and noticed a strange problem. After installing WOAI's Icelandair package, I was flying around Aerosoft BIKF during summer, and noticed no Icelandair planes even though reading the AI's flight plan file, there should have been lots of Icelandair planes there at that time. So then I reset the date back to current day and the time to the same GMT that I was flying before, after doing that, all of the Icelandair planes that were supposed to be there were there that time. So my question is, are AI flight plans dependent on the time of year set in sim? Or is there another reason why the AI wasn't showing up during the summer even though in both tests I was using the exact same GMT time? I was under the impression that AI flight plans followed GMT as programmed in the flight plan file, but this does not seem to be the case...