The Yankee Clipper project dated back to 1935, with the start of a series of negotiations between Pan American World Airways and Boeing for the production of a flying-boat capable of guaranteeing transatlantic passenger flights with a high degree of safety, comfort, and speed.¹ On July 21,1936 Pan American signed a contract for six aircraft, the first of which (designation Model 314) made initial see runs on Puget Sound on May 31,1938, and took to the air on June 7, 1938. ² When it made its appearance this flying-boat was the largest civil aircraft in service.

When the Boeing 314 flying boat first made its appearance, it was the largest civil aircraft in service. The aircraft shown above is the California Clipper

It outstripped all rivals in size, with twice the size of the Sikorsky S-42 and outweighed the Martin M-130 China Clipper by 15 tons.³ The 14-cylinder double-row Wright Cyclones were the first to use 100-octane fuel. The Boeing 314, the finest flying boat to go into regular commercial service, weighed 40 tons, and the first batch cost $550,000 per aircraft.

It had a central hull and adopted the wing and engine assembly of the experimental Boeing XB-15 heavy bomber. In the place of the traditional floating stabilizers at the wingtips, sponsons mounted on the sides of the hull were used. The sponsons were based on the formula developed by the German engineer Claude Dornier and incorporated into such aircraft as the Dornier Do X and Dornier Do 18. The sponsons also contained fuel tanks, the capacity of which (together with those situated in the wings) totalled almost 3,525 gallons (16,000 litres).

Mechanics performing maintenance repairs on the California Clipper. The number on the centre vertical stabilizer is No 18 and the number on the left hand vertical stabilizer is NC 18602

At first, Boeing had problems with the single vertical stabilizer, which resulted in inadequate directional control. It tried a twin-tail arrangement, and finally settled on the three fins which became a feature of the design.

In the spacious fuselage there was ample room for 74 daytime passengers, or for 40 passengers in reclining seats for long night-flights.

On May 20,1939, Pan American inaugurated the first transatlantic mail service. Under the command of Captain A. E. LaPorte, almost a ton of mail was carried from Port Washington to Marseilles, via the Azores and Lisbon. in 29 hours. The same aircraft, commanded by Captain Harold Gray, opened the northern mail service to Southampton on June 24,1939.

On June 28,1939 Pan American inaugurated the first regular passenger service, from New York to Southampton, via Newfoundland. Under the command of Captain R.0.D. Sullivan, the "Dixie Clipper" carried the first scheduled passengers across the North Atlantic. Twenty-two privileged persons had the option of paying $375 one-way (about $4,000 in today's money) or $675 return (say about $7,000 or $8,000, or twice Concorde levels). The Yankee Clipper opened the northern passenger route on July 8,1939, carrying 17 passengers at the same fare. Today, the North Atlantic route is still the most prestigious of all today despite the immense growth of the airlines.

The golden age of the commercial flying-boats was abruptly interrupted by the outbreak of the Second World War in Europe on September 3,1939. The war curtailed Pan American's opportunity to build on its success, The northern transatlantic route was abandoned after only three months, on October 3,1939.

With the success of the Boeing 314, Pan American ordered another six with the designation Boeing 314A. The 314A was considerably improved. They had a carrying capacity (77 daytime passengers), engine power, and increase in fuel capacity by about 1,000 gallons (4,500 litres). The first of the Boeing 314A aircraft flew as a prototype on March 20, 1941, but with WW II in full swing, only half the order went to Pan American. Three models were bought by the British government and allotted to BOAC for use as transport aircraft.

Aircraft shown is the Atlantic Clipper. The number on the left hand vertical stabilizer is NC 18604

Subsequently, the Boeing 314s continued flying all over the globe, maintaining especially the Atlantic crossing by the central route, or via Brazil and West Africa. They made many important flights during the war, in support of military operations as far afield as southeast Asia. The Boeing 314 airplanes were well known for the fact that they carried Winston Churchill on his intercontinental journeys, and survived the war to be returned to the United States in 1948.

The career of the Boeing 314s, five of which were purchased by the USAAF and the US Navy, was also a lengthy one. Apart from three which were destroyed in February 1943, November 1945 and October 1947, the others remained with Pan American. With the progress made in developing long-range landplanes during WW II, the last Boeing 314 was retired from Pan American World Airways in 1946. They were then used by various small charter companies and not withdrawn from service until 1950.