When the airlift began, there were only two airfields in Berlin; Tempelhof with one runway in the US sector and Gatow with one runway in the British sector. In 1945, when the Americans arrived in Berlin, Tempelhof's lone runway was sodded and had been used only for small aircraft and fighters during the latter stages of World War II. It was beautifully equipped with hangars and a large terminal building, but it was surrounded by high apartment buildings which required a 500 foot ceiling in thick weather. Before June 1948, US Army engineers had built a 12 foot thick rubber base runway and covered it with steel landing mats which was adequate for US military needs before the airlift. However, under the continuous pounding of heavy, loaded aircraft the steel landing mats started to break. Depressions in the runway began to form and soon a force of 225 men was kept busy working on the runway between plane landings in attempting to keep the field operational. In early July 1948, construction on a new runway at Tempelhof began without interrupting airlift traffic and during the same period the old runway was being constantly repaired. In late 1948, construction began on a third Tempelhof runway.