According to the specs for Access-Control, using a 'POST' to a cross-domain should not trigger an OPTIONS pre-flight. Unless there are non-standard headers that is.

http://www.w3.org/TR/2007/WD-access-control-20071126/

https://developer.mozilla.org/en/HTTP_access_control

These two lines in jquery.js set a custom header, and cause a preflight OPTIONS request:

Set header so the called script knows that it's an XMLHttpRequest

xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");

Would be great if it could be either disabled by default for cross-domain requests, or removed completely, or made optional with a provided switch to toggle it on and off.

Same bug in Dojo: http:trac.dojotoolkit.org/ticket/9486