ajax loading 2 XML documents in order without async:false

I am loading 2 XML documents that both run functions on success, although the function for the 2nd XML document is dependant on the 1st being complete.

If I have async:true:

function XmlDataTypes() {

var result = null;
var scriptUrl = "http://ift.tt/16yCsKj" + AccountId;
$.ajax(
{
    url: scriptUrl,
    type: 'get',
    dataType: 'xml',
    async: true,
    success: function (data) {



    },
    error: function onXmlError() {
        alert("An Error has occurred.");
    }

});

return result;

}

The XML data can loaded in a random order so the function for the second document will error if the 1st hasn't completed.

If I set:

async: false

It works correctly but I get a warning:

Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience.

Is there a way around this without using:

async: false