Were they having wrong altitude or speed readings maybe ? Perhaps a pitot or a static blocked causing confusing read outs in the cockpit ? The controller can't help in that situation, you have the same info in both places ( the cockpit and the controller's radar screen ), the controller screen shows data received from the aircraft's transponder, so if you have a pitot or a static/port blocked the controller probably has the same wrong information you have in the cockpit. This problem occurs in two deadly accidents ( Birgenair for a pitot and Aeroperú for the static, both times 757 ). The only way you can get a reliable source in a situation like that is another aircraft flying next to you and telling your speed and altitude...Aeroperu's crew request that help but sadly they crashed before a cargo jet reach them.
Last edited by Jetdriver; 3rd Aug 2011 at 15:25.