很容易试试这些
Ext.Ajax.request({
    method:'GET',
    contentType:'application/json; charset=utf-8',
    dataType:'json',
    url:'http://..................Login',
    disableCaching: false,
    withCredentials: true,
    useDefaultXhrHeader: false,
    callbackKey: 'callback',
    params: {
        xyz:.......                                              
      },
    success:function(response){
        console.log(response);
        var res = response.responseText;    
        var jsonarr = Ext.decode(response.responseText);
        console.log(jsonarr);
        var myres = jsonarr[0].Result;
        console.log(myres);
        Ext.Viewport.setMasked(false);  //hide the mask  loaded ...
       Ext.Viewport.setActiveItem({xtype:'dom_flightlist'}); 
   }//end of success fn
}); //end of AJAX Request
在成功函数之后添加负载掩码..