Hi CaptainTomMurray,
not sure why it is redirecting you to Adobe's main page. Here are direct links to the installers:
» https://airdownload.adobe.com/air/win/download/21.0/AdobeAIRInstaller.exe (Windows)
» https://airdownload.adobe.com/air/mac/download/21.0/AdobeAIR.dmg (Mac)
Hope that helps
Kind Regards,
Maurice