After a second season flying his Lockheed Vega in Antarctica Wilkins planned his most ambitious expedition. To take a submarine under the Arctic ice to the North Pole. Constant delays prevented the submarine getting away on time to reach the polar ice cap before winter and the submarine constantly broke down. Still determined to prove that submarine travel under the ice was possible, Wilkins continued north to the edge of the ice pack to discover his submarine had malfunctioned again. Nevertheless, with his partly disabled submarine he was still able to sail under the ice to prove it could be achieved.