Experience showed that there was a need for widespread use of aircraft which could not be met quickly enough by building new fleet aircraft carriers. This was particularly true in the North Atlantic, where convoys were highly vulnerable to U-boat attack. The British authorities used unorthodox, temporary, but effective means of giving air protection such as CAM ships and merchant aircraft carriers, merchant ships modified to carry a small number of aircraft. The solution to the problem were large numbers of mass-produced merchant hulls converted into escort aircraft carriers (also known as "jeep carriers"). These basic vessels, unsuited to fleet action by their capacity, speed and vulnerability, nevertheless provided air cover where it was needed.