A little more than four years ago, Ticos preparing to go to the polls in early February noticed that the skies above the Central Valley were crisscrossed by contrails (condensation trails, those fluffy white lines that airplanes leave behind). Claudia Calvo, a resident of Curridabat in the eastern suburbs of San Jose used her mobile phone to capture video of the sky along with her observations about sudden weather changes and dead birds she found the next day. Ms. Calvo believes this was evidence of a “chemtrail episode” in Costa Rica, which is something that has become even more common in the big sky above Guanacaste.

The chemtrail phenomenon is part of a conspiracy theory that proposes that not all vapor lines in the sky are contrails. Chemtrail supporters believe that there may be trails of chemical or biological substances sprayed by shadowy entities for ulterior purposes. One of these believers is William Vander Zalm, former Premier of British Columbia Canada, whose comments on chemtrails being associated with secret “geoengineering” projects such as weather manipulation were recently published by alternative media site Collective Evolution:

I believe it’s been going on for some time, but to what extent and how much the government knows about it, I don’t know. Chemtrails are happening all over the world, just exactly who’s engineering all of this I don’t know and that’s exactly what I’m trying to find out. Governments do things without asking, and we find out about it when it’s too late.

Residents of Guanacaste who subscribe to the chemtrails conspiracy theory are concerned by the number of fluffy white lines in the sky. To support their claims, they post videos on YouTube along with their concerns over possible nefarious motives such as population control or weather modification experiments.

When Ms. Calvo filmed evidence of multiple persistent contrails over Costa Rica around election day four years ago, she remarked that the phenomenon occurred at the time a vaccination campaign against swine flu was about to begin. She pondered if the chemtrails were somehow related to this prophylaxis. The problem with this conjecture is that contrails typically form at an altitude of eight kilometers, and anything sprayed at an altitude of 800 meters or higher would never reach the intended targets.

The reason contrails (or chemtrails, if you will) are often seen in Guanacaste is because this province enjoys nearly year-round postcard weather, which means cloudless skies are not so uncommon. With reduced cloud coverage, tourists and expat residents in Guanacaste are more likely to enjoy fluffy white lines against gorgeous blue skies on many days of the year.