How does Boeing name their planes, such as Boeing 747? Why do they call it 747?

You must have noticed that all Boeing’s commercial aircraft names are in this format i.e. 7-7 (starts with 7 and ends with 7). This 7-7 designation which has come to signify Boeing’s line of commercial jets was chosen for purely marketing purposes.

Before the WW2 ended, company only used to manufacture military aircraft. After WW2 the company decided to turn its attention to building commercial planes. When the age of jet engines started in 1930-40, the company started building jet powered military aircraft (B-47 Stratojet (Model 450) and B-52 Stratofortress (Model 464)).These two aircraft made Boeing the nationally-recognized leader in the design and construction of large, jet-powered aircraft. And that is when the company decided to build country’s first commercial jet airliner.

The effort began when Boeing initiated a study of a turbojet-powered version commercial version of the KC-97 Stratofreighter (Model 367). But they had a problem. The company knew that airlines (USAF and others) would not commit to the enormous development costs required. Boeing instead hoped that the US Air Force would fund for this project. Unfortunately, the Air Force showed no interest in the proposal, and it was rejected in 1951. Boeing instead decided to commit over $15 million of company funds to develop this project, convinced that the USAF would eventually buy it anyway. Since this design was inspired from KC - 97 Model 367 and in an effort to maintain secrecy, the new project was named as Model 367-80, popularly known as the “Dash-80” by Boeing employees.

The Dash-80 soon evolved far beyond its initial concept. The design ultimately became much larger, with a longer, wider, and more streamlined fuselage able to hold 130 passengers. By the time the Dash-80 made its first flight in 1954, the Air Force had changed its mind about the project and soon ordered 29.

But the USAF and other airlines interest was somewhat slow in coming, so Boeing officials looked to give the project a new, more memorable name. The Model 367-80 had never been intended as anything more than an internal designation. Models in the 500s had been reserved for gas turbine engines and the 600 series for missiles (as I have already mentioned in the start of this answer). The 700 series was already decided to be used for commercial aircraft, so the company board decided to officially rename the Dash-80 as the Model 707. That is how the series 7-7 started (the reason was completely marketing related). The later versions/aircraft 727, 737, 747, 767, 787 are the variants (improved/developed/advanced/flexible versions) of 707.

After World War II, one of the largest aircraft manufacturers, Boeing, turned its attention from designing military craft to building commercial planes, along with missiles and spaceships. (Unrelated fact: when Boeing was forced to spin off its passenger flight division, the newly-formed company became United Airlines.

Back to the late 1940s: Model numbers were assigned to each division of aircraft (from the Boeing website:) “300s and 400s represented [military] aircraft, 500s would be used on turbine engines, 600s for rockets and missiles and 700s were set aside for jet transport aircraft.

The company’s marketing department felt that the number 700 didn’t have enough pizzazz. So the first commercial passenger airline in the series was assigned the number 707 (pronounced Seven Oh Seven). The Boeing 707 is credited with launching the beginning the “Jet Age.”

It was decided that all model numbers that either began or ended in a “7” would be reserved for commercial jets.

The most well known aircraft in the 7×7 series is the Boeing 747, which also goes by the nickname “jumbo jet.” The 747 made aviation history. It was designed in the 1960s as a response to an increase in air traffic. It was the largest civilian airplane in the world.

To construct the massive 747, Boeing used a 200-million-cubic-foot assembly plant in Everett, Washington. According to the Boeing site, the total wing area of the original 747 was larger than a basketball court. And its gross weight was 735,000 pounds.

There are Boeing 757s 767s, 777s (the “Triple Seven,”) but the 737 and 747 are most ubiquitous in the public imagination. In 2009, the 787, the “Dreamliner,” made its debut flight.

 
Hope this helped.