I'm not sure if it works in all browsers, but for me at least, even http://ai is enough to reach the site.
But wtf, Firefox redirects it to uniregistry.com :o
Same thing on mobile, but it's taking you to `ai.com` first, and then redirects to Unregistry as it looks to be for sale.
And as another commenter has stated `http://ai.` works as expected in FF.