The UAL Mainliner is framed with the San Francisco-Oakland Bay Bridge, Yerba Buena Island and Treasure Island, which only looked like this during the 1939-1940 Golden Gate International Exposition. No Pan Am flying boats are visible in the Clipper Cove between the two islands. Treasure Island was to become a land airport after the fair, but became a naval facility instead. NC16087 flew for UAL until 1955. As PI-C942 it crashed in the Philippines in 1965. Photo from: SFO Museum

Pan American's Consolidated "Commodore" on exhibit as part of the 1940 Golden Gate International Exposition. Carried "Training Plane No.1" on the nose. The exposition opened May 25, 1940, through September 29, 1940.

A new Boeing 314, NC18603, at Pan American's Treasure Island base, wearing fleet number 17. Given the amount of people, the photo seems to have been taken during the Golden Gate International Expo which opened here on 18 February 1939. The aircraft flew to Baltimore five days later to join Pan Am's Alantic Division, and was christened Yankee Clipper by Eleanor Roosevelt in Washington, DC on 3 March. Photo from: San Francisco Public Library

In flight over San Francisco. The 1939-1940 Golden Gate International Expo is under construction on Treasure Island, with the Pan Am flying boat terminal on the right side. As N16070 this DC-3 is preserved in the Evergreen museum in McMinnville, Oregon. Photo by: Carl Mydans / Life

Overflying Pan Am's new seaplane terminal on Treasure Island. All buildings of the Golden Gate International Exposition were razed down in 1940 to make room for a new land airport, but it became a naval facility instead. This is the second Boeing 314 airframe, the first to fly with triple tailfins. Named California Clipper, it was approaching Auckland in New Zealand on a regular transoceanic flight on 7 December 1941 when news came in of the Japanese attack against Pearl Harbor. Captain Robert Ford was ordered to proceed westward to New York and managed to complete an amazing 50,000 km trip via Australia, Java, Ceylon, Karachi, Bahrain, Sudan, Congo and Brazil. Photo from: SFO Museum