Project Habakkuk or Habbakuk (spelling varies) was a plan by the British during the Second World War to construct an aircraft carrier out of pykrete (a mixture of wood pulp and ice) for use against German U-boats in the mid-Atlantic, which were beyond the flight range of land-based planes at that time. The idea came from Geoffrey Pyke, who worked for Combined Operations Headquarters. After promising scale tests and the creation of a prototype on Patricia Lake, Jasper National Park in Alberta, Canada, the project was shelved due to rising costs, added requirements, and the availability of longer-range aircraft and escort carriers which closed the Mid-Atlantic gap that the project was intended to address.