In the middle of the Second World War the British government explored an idea so unusual that it might seem unbelievable. The plan was to build a massive aircraft carrier made not from steel but from a reinforced ice-like material and use it as a floating air base in the Atlantic Ocean. This idea was given the code name Project Habakkuk and involved scientists, engineers, and military leaders working together in a classified wartime program to address a critical strategic problem.
The Mid-Atlantic Gap and the Habakkuk Concept
German submarines were attacking Allied shipping in the mid-Atlantic where land-based aircraft could not reach. This area was called the Mid-Atlantic gap and it posed a serious threat to the supply routes between the United States and Britain.
Conventional aircraft carriers were not available in sufficient numbers and steel was in short supply for building more warships. In early 1942 British strategist Geoffrey Pyke proposed building a floating platform from ice reinforced with wood pulp and other materials. This composite material was later named pykrete.
Pykrete had properties that made it stronger than plain ice and slower to melt. Scientists such as Max Perutz conducted tests to determine whether a large pykrete vessel could survive in ocean conditions. They envisioned a ship with walls up to 40 feet thick and a runway over 600 metres long that could carry dozens of aircraft. Plans even included armaments and internal systems that would allow the vessel to operate in harsh Atlantic weather.
Building and Testing the Prototype
In 1943 a large-scale model was built at Patricia Lake near Jasper National Park in Alberta, Canada. The prototype measured about 60 by 30 feet and weighed around 1,000 tons. It was constructed by workers who were conscientious objectors fulfilling alternative service. The prototype included a basic refrigeration system to keep the pykrete frozen and to test the material’s behaviour under controlled conditions.
During this period military leaders demonstrated the strength of pykrete in dramatic fashion. At the Quebec Conference in 1943 Lord Louis Mountbatten brought blocks of ice and pykrete to a meeting attended by Allied leaders. He showed how conventional ice shattered when struck by bullets, while pykrete resisted impact. On one occasion a bullet fired at pykrete ricocheted and grazed the leg of a naval officer present.
Why the Project Ended
Despite the promise shown by the prototype and the theoretical strength of pykrete, practical challenges and changing conditions made the project unworkable. The cost of building a full-size pykrete aircraft carrier rose dramatically as requirements increased.
Scientists found that a refrigeration plant and insulation would be necessary to prevent sagging and melting of such a large structure. At the same time the threat from German submarines was diminishing because of improved long-range aircraft, the establishment of air bases in the Azores and Iceland, and the increasing number of escort carriers. These developments reduced the need for a floating air base in the mid-Atlantic.
By the end of 1943 the decision was made to terminate the project. The prototype was left in the lake and eventually melted over successive summers. No full-scale pykrete vessel was ever constructed, and the idea remained a fascinating chapter in the history of wartime engineering.
In World War II Britain explored a plan to build an aircraft carrier from ice.
Project Habakkuk aimed to solve deadly Atlantic shipping losses using a floating air base so vast it sounded impossible yet moved into real tests…🧵👇 pic.twitter.com/oXYNdy9gDe
— Fascinating True Stories (@FascinatingTrue) December 22, 2025