The hunt for the Malaysian plane suffered another setback on Apr 16 when a second seabed search by the mini-submarine launched from the "Ocean Shield" was cut short due to technical troubles after the first also aborted in very deep water. The first mission which began in the night of Apr 15 aborted automatically after breaching the machine’s maximum operating depth of 4,500 metres. There was no explanation for what caused the interruption of the second mission, which began the following night when the Bluefin-21 was forced to resurface to rectify a technical issue. The Bluefin-21 was then redeployed and was continuing its underwater search. Before the device was put in the water for the third time, data had been downloaded from the vehicle while on the deck of the "Ocean Shield". Initial analysis of the data downloaded indicated no significant detections. The US Navy has estimated it would take the Bluefin-21 between six weeks to two months to scan the entire search area which had been narrowed down using satellite data and the detection of electronic pulses from the black box which were last heard more than a week ago. The visual search for debris also continued with as many as 14 aircraft and 11 ships involved over an area of 55,151 square kilometres more than 2,000 kilometres northwest of Perth.