The British had about 150 C-47 Dakotas and 40 Avro Yorks. The RAF was also using 10 Short Sunderlands and later by Short Hythe flying boats. These flew Finkenwerder on the Elbe near Hamburg to the Havel river. The flying boats were designed to resist rust and water damage so were very useful for transporting bulk salt, which would have rusted the other planes. Many other aircraft were later used, and the British had flown in about 100,000 tons of cargo by the end of the blockade.