In June 1948, Joseph Stalin halted all road and rail traffic in to and out of the Allied sector of Berlin and cut off all electricity to the city. The only route into Berlin was by means of three twenty-mile-wide air corridors across the Soviet zone of Germany. Thus the wartime allies of Britain, France and the USA realized that the only option open to them was to supply the beleaguered West Berlin by air transport and so started one of the most dramatic events of the twentieth century. The airlift started in June, 1948. At the beginning there were three loading airfields: Rhein Main and Wiesbaden in the American zone, and Weinstorf in the British zone. By September of 1948 the airlift was transporting a massive tonnage of supplies into Berlin, including coal, food, medical supplies and all the other necessities of life. A mixed fleet of aircraft plodded their endless path to and from the city. Both Ex-planes and pilots were dragged out of retirement. In September 1948 the Russian military threatened to force down western aircraft if they flew outside the 20-mile wide corridors but by March 1949 a total of 45,683 tons of supplies per week were being flown into Berlin. In April Russia finally announced her intention to end the blockade.