I hope that you enjoy using Plane Finder!
There is no download for Plane Finder to the PC or Laptop. Plane Finder is only accessible on PC's and laptops by the site: www.planefinder.net
There is a download for Plane Finder on iOS and Android devices. Plane Finder is only available for download as a app on iPhone and Android and Plane Finder HD is available for download on iPad. The team at Plane Finder does have other applications to offer on both of these devices like Ship Finder and Airline Finder.
I have no idea of a download being possible for computers. I think this question should be answered by one of Plane Finder's helpful administrators.
I hope that this answers your question!
If there are any more questions that you may have to ask, I am happy to answer them!