West Berlin could be blockaded on the ground but not sealed from the air.
On June 24, 1948, Soviet forces blocked rail, road, and water access to the Allied-controlled sectors of Berlin.
The United States and Britain answered by flying food and fuel from airbases in western Germany.
Keeping that schedule meant tight spacing, quick unloading, and enough daily tonnage to make the air corridors into a supply line.
The airlift did not make the blockade harmless. It kept West Berlin supplied until land access reopened in May 1949.