Boeing 707 and C-135 family
When the jet age for passenger transport aircraft commenced in the late 1940s with the deHavilland Comet, Boeing started studies for their own jet transport. At the same time it wanted to respond to a requirement from the US Air Force for a jet aircraft capable of refuelling fast fighters and bombers. This led to a concept aircraft, known as model 367-80. This aircraft formed the basis for both the Boeing 707 and 720 commercial transports and the military C-135 line.
Like contemporary aircraft both models have a conventional configuration with low, swept wings, horizontal stabilisers attached to the rear fuselage and four jet engines in pods under the wings. The key distinctive features on the Boeings are the two eyebrow cockpit windows on each side and V shape of the lower end of the cockpit side windows. Finally nearly all aircraft have an HF antenna pointing forward from the top of the vertical stabiliser.
How to recognise the different versions of the civil and military Boeing 707s, 720s and C‑135s will be added later.
Confusion possible with
The Shanghai Y-10 has most resemblance to the Boeing 707/720, as it formed the basis for the Chinese reverse engineered aircraft. The main differences are in the nose shape, cockpit windows and lack of antenna on top of the tail. (photo: Zhangmingda/WikiMedia)
The Douglas DC-8 is from the same time frame and looks similar. This aircraft can be recognised by the single eyebrow cockpit window on each side, air intakes at the lower side of the nose and the lack a forward pointing antenna on top of the vertical stabiliser.
The Convair 880 and 990 are more easily confused with the DC-8, but they look like 707s and C-135s as well. A look at the nose and tail is enough to keep them apart, as the Convair aircraft have no eyebrow cockpit windows, no air intakes in the nose and no antenna on the tail.
The slim engine nacelles may fool you but the Il-86 is much bigger than the Boeing 707; it is a wide body, while the Boeing is a narrow body aircraft. Like the aircraft types described above it also lacks the distinctive cockpit windows and tail of the Boeings.