Boeing 307 facts for kids

Kids Encyclopedia Facts

Quick facts for kids Boeing 307 / C-75

A Boeing 307 at the Steven F. Udvar-Hazy Center
Role	Airliner
Manufacturer	Boeing
First flight	31 December 1938
Introduction	8 July 1940
Retired	1975
Status	Retired
Primary users	TWA Pan Am United States Army Air Forces
Number built	10
Unit cost	$315,000 (in 1937)
Developed from	Boeing B-17 Flying Fortress

The Boeing Model 307 Stratoliner was a special airplane built by Boeing. It was the first airliner to have a pressurized cabin. This meant the Boeing 307 could fly very high, at about 20,000 ft (6,000 m). Flying this high allowed it to go above most bad weather. Inside the plane, it felt like you were only at 8,000 ft (2,440 m), even when the plane was much higher.

The Model 307 could carry five crew members and 33 passengers. Its cabin was almost 12 ft (3.6 m) wide, which was quite big for its time. It was also the first land-based plane to have a flight engineer as part of its crew.

Building the Stratoliner
- The C-75 Military Version
History of the Stratoliner
- C-75 Military Routes
Different Types of Boeing 307
Who Used the Boeing 307?
- Civilian Users
- Military Users
Boeing 307s Still Around
Related pages
Images for kids
See also

Building the Stratoliner

In 1935, Boeing started designing a new four-engine airliner. This plane was based on the famous Boeing B-17 Flying Fortress bomber. It was called the Model 307. It used the same wings, tail, rudder, landing gear, and engines as the B-17C.

However, the main body of the plane was different. It was shaped like a perfect circle, about 138 in (350 cm) across. This round shape was important because it allowed the cabin to be pressurized.

The first company to order the plane was Pan American Airways in 1937. They ordered more planes later. Another airline, Transcontinental & Western Air (TWA), ordered five of these new aircraft. Boeing then began building the planes.

The C-75 Military Version

When the United States joined World War II in December 1941, flying became very important for the government and military. Long-distance flights were needed for officers and supplies. Planes like Pan Am's flying boats and TWA's five Boeing 307s were used for this.

To fly further, extra fuel tanks were added to the planes. These military versions of the Boeing 307 were called C-75s. Before the war stopped production, 10 Stratoliners had been built for airlines. TWA flew their planes between New York and Los Angeles for 18 months. Then, the U.S. Army bought their planes.

TWA changed their 307s into C-75s in January 1942. These C-75s were the only American planes that could cross the Atlantic Ocean with cargo. This was true until the Douglas C-54 Skymaster was made in November 1942.

For military use, the C-75s had their special pressurization equipment removed. This made the plane lighter. Some seats were also taken out, and other changes were made. Five large fuel tanks, each holding 212.5 U.S.gal (804 L), were added. The landing gear was made stronger, and the plane could carry more weight when taking off. The outside of the planes was painted olive drab, a military green color.

History of the Stratoliner

The very first Boeing 307 Stratoliner flew on December 31, 1938, from Boeing Field in Seattle. Sadly, this first plane crashed on March 18, 1939, while the airline KLM was testing it.

The first delivery of a Stratoliner was to Howard Hughes. He bought one Boeing 307 because he wanted to fly around the world faster than ever before. Hughes' plane had extra fuel tanks for this long journey. It was ready to go, but then Nazi Germany invaded Poland on September 1, 1939. Because of the war, Howard Hughes did not make his flight. This 307 later had its extra fuel tanks removed and more powerful engines added. It was supposed to be a fancy "flying penthouse" for Hughes, but he didn't use it much. It was eventually sold.

Pan Am started receiving its Boeing 307s in March 1940. TWA got its first 307 in April. TWA used its 307s to fly from Los Angeles to New York. Pan Am's planes flew from Miami to Latin America.

In total, ten 307s were made. Three went to Pan Am, named Clipper Flying Cloud, Clipper Comet, and Clipper Rainbow. Five went to TWA, named Comanche, Cherokee, Zuni, Navajo, and Apache. One went to Howard Hughes. The very first 307 built was the one that crashed.

After the United States joined World War II, Pan Am continued to fly its planes to Central and South America. However, the Army Air Force was now in charge of these flights. TWA's Boeing 307s were sold to the U.S. government. They were called Boeing C-75 and were used by the United States Army Air Forces.

An Aigle Azur Stratoliner at Paya Lebar in 1967

The U.S. Army gave the five C-75s back to TWA in 1944. TWA sent them back to Boeing to be rebuilt. Boeing replaced the wings and put in more powerful engines. The electrical systems were updated with parts from the Boeing B-29 Superfortress. After these changes, the 307 could carry 38 passengers. TWA later switched to the Lockheed Constellation, but the 307s were used until April 1951. TWA then sold its Stratoliners to a French airline called Aigle Azur.

C-75 Military Routes

The C-75 military planes flew two main routes during the war. One route was from Washington, D.C. to Cairo, Egypt. The other was from New York to Scotland. Sometimes, they flew from Gander, Newfoundland to Prestwick, Scotland. They also flew between Natal, Brazil and Accra, Ghana. After July 1942, they could stop to refuel at Ascension Island.

Different Types of Boeing 307

Passengers on a Pan Am Boeing 307

Royal Air Lao Boeing 307 Stratoliner

307: This version had Wright Cyclone GR-1820-G102 engines and a crew of five.
307B: This version had Wright Cyclone GR-1820-G105A engines and a crew of seven.
C-75: These were Boeing 307s that were used by the U.S. military during World War II.

Who Used the Boeing 307?

Civilian Users

France Aigle Azur
Laos Royal Air Laos
United States Howard Hughes (bought one plane)
United States Pan Am (had three planes)
United States TWA (had five planes)

Military Users

Haiti Haitian Air Force
United States United States Army Air Forces

Boeing 307s Still Around

Boeing 307 (NC 19903) in Elliott Bay, Seattle, March 28, 2002

The only complete Boeing 307 Stratoliner that still exists is at the Smithsonian Museum's Steven F. Udvar-Hazy Center. On March 28, 2002, this plane was badly damaged when it had to land in Elliott Bay in Seattle, Washington. This was its last flight before it went to the Smithsonian for display.

The main part of Howard Hughes' 307 also still exists, but it has been turned into a house boat.

Aircraft related to this one

Boeing B-17 Flying Fortress

Images for kids

Boeing S-307 Stratoliner production line - note the early B-17s to the rear
Prototype Model 307 NX19901 with the small tail as initially designed, and which caused its loss.
Wreck of the prototype, NX19901
TWA Boeing SA-307B NC19905 on May 17, 1940 after the engines iced up and it made a forced landing
TWA Boeing SA-307B NC19907 'Zuni' 402 landing with slotted flaps lowered, prewar
Pan Am Boeing S-307 Stratoliner NC19902 Clipper Rainbow with blanking plates installed on engines to prevent engine over-cooling
Newly graduated Hostesses lined up in front of Zuni, TWA's Stratoliner NC19907, in early to mid-1940.
42-88623 Cherokee loading up following conversion to C-75 standard
Prototype of the S-307, with the small tail used initially on the first three examples built.
Ex-Pan Am Inter-American Inc. Boeing S-307 Strato-Clipper N19903 after returning to the US from Haiti, before being bought by the Smithsonian.
T&WA Boeing SA-307B Cherokee as built.
Boeing 307 prototype from above, showing off the wing and tail planform
TWA Boeing SA-307B NC19905 Comanche undersides, showing off just how wide the 11.5 ft (3.5 m) fuselage was. The external arms for the slotted flaps are visible here, as are the hatches on the underside through which baggage was loaded.
Map of 1940 TWA Boeing 307 routes
USAAF C-75 42-88624 Comanche in wartime camouflage
Boeing C-75 ICD primary wartime transatlantic routes after July 1942, when the airfield as Ascension Island shortened the South Atlantic crossing. Bluie Two and Eight were added in 1942 as diversionary airfields in case excessive headwinds were encountered in the North Atlantic. When conditions allowed it, usually on summer eastbound crossings, direct flights were sometimes made between Gander and Prestwick.
TWA Boeing SA-307B-1 N19909 'Navajo' fleet number 404, as it appeared when offering coach class seating only, and showing the rearward location of the higher aspect ratio B-17G tailplane, whose hinges were now lined up with the rudder hinge.
Lineup of all three Pan Am Strato-Clippers
Aerovias Ecuatorianas C.A. (AREA) Boeing S-307 Strato-Clipper HC 004
Aigle Azur Extrême-Orient Boeing S-307 Strato-Clipper F-BHHR in New York just before delivery
Aigle Azur Boeing SA-307B-1 F-BELV on the ramp
Airnautic Boeing SA-307B-1 F-BELY
Boeing SA-307B-1 Stratoliner F-BELX, likely while with Cambodia Air Commercial
SA-307B-1 F-BELU with the CIC/ICC
Pan Am Boeing S-307 Strato-Clipper NC19910 Clipper Comet
TWA Stratoliner pre-war, at Chicago airport
Quaker City Airways Boeing S-307 Stratoliner N75385
UAT Aeromaritime Boeing SA-307B-1 F-BELV
Restored ex-Pan Am Stratoliner NC19903 displayed in the Steven F. Udvar-Hazy Center
Boeing SA-307B Stratoliner 3-view drawing