Summary

  • The Boeing 720 stands out among Boeing's commercial jets due to its name ending in zero, unlike the usual number system starting and ending with seven.
  • The model numbering system for Boeing's commercial planes began after World War II, with different blocks of 100 assigned to each department.
  • The Boeing 720 was named this way because the original model number, 707-020, was changed to avoid negative publicity for United Airlines, the first carrier to fly the plane.

The Boeing 720 is an anomaly among Boeing's commercial jets. With the United States-based aircraft manufacturer favoring a number system that starts and ends with seven, a name ending with zero sticks out. So, why did the company choose to name the plane this way? Let's look at the journey of how the jet and its title came about.

Putting a structured system in place

After World War II, Boeing was a military airplane enterprise. William Allen, Boeing's president at the time, felt it was time to venture back into the commercial realm. However, it still wanted to make progress in other aspects, such as with missiles and spacecraft.

So, amid this diversification of products, the company's engineering team segmented model numbers into blocks of 100 for each department. 300 and 400 were implemented for commercial propeller-driven planes, while 500 was introduced for turbo-engines. Subsequently, Boeing used 600 for missiles and rocket-powered devices.

The firm developed the first large swept-wing jet in the world with the B-47. Even though this plane was a military legend, airlines also showed interest in the model. Notably, Pan Am asked Boeing to look into the prospects of applying the aircraft as a commercial jet. Meanwhile, the manufacturer was also studying converting the propeller-driven model 367 Stratotanker, better known as the KC-97, into a jet-powered tanker that would keep up with the B-52 during inflight refueling.

A catchy name

Boeing's development team went through several editions of the model 367 before settling on a variant numbered 367-80. This model would go by the moniker of Dash 80, which first took to the skies in 1954.

The aircraft would mark the transition into the familiar Boeing numbering system that we are all familiar with - the 7-7 formula. This factor would also contribute to the eventual naming of the 720. As Boeing Frontiers explains,

“Boeing took a calculated risk by financing the development and construction of the Dash 80 prototype with its own funds. The goal was to put the airplane into production as both an Air Force tanker/transport and a commercial jet transport. Since both of these offspring of the Dash 80 would be jet transports, the model number system called for a number in the 700s to identify the two new planes. The marketing department decided that "Model 700" did not have a good ring to it for the company's first commercial jet. So they decided to skip ahead to Model 707 because that reiteration seemed a bit catchier."

Taking on the industry

The Boeing 707 entered service with Pan Am in October 1958, setting the standard for Boeing's commercial jets in the following decades. In only a few years, air travel had surpassed rail and sea travel with the assistance of this plane. Boeing was also happy to modify the type to suit the needs of its clients - it built rare long-range customizations for Qantas and even installed larger engines for Braniff when the airline flew to high altitudes in Latin America.

One of these modifications was the 720 - this variant had its fuselage length shortened by 9 feet (2.7 meters) to take on short-to-medium-range operations and for use on shorter runways. Along with this, the leading edge flaps were switched before turbofan engines were equipped.

Taking care of the customers

In hindsight, there was a noticeable oddity to the Boeing commercial jet numbering process with the 720, particularly as the plane was first promoted to carriers as the model 707-020. United Airlines was keen on taking on this model - however, it had previously decided to go with Douglas' DC-8. Therefore, to help the Chicago-based carrier avoid negative public relations for reverting to the 707, Boeing Frontiers explains that the planemaker changed the entire name. Thus, the 720 was born.

The 720 made its maiden flight on November 23rd, 1959, and was subsequently introduced on July 5th, 1960. In total, 154 units were built between 1958 and 1967, with United Airlines as the first carrier to fly the plane. Boeing's tailored approach with the 707 range paid off, with both the 707 and the 720 overtaking the DC-8 in sales.

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A successful series

Altogether, Boeing's commercial jets - apart from the 720 - were named in succession based on the 7-7 formula. The 707, 717, 727, 737, 747, 757, 767, and 777 have all gone by this code, and its latest commercial jet, the 787 Dreamliner, carries on the trend. The 720 may be one of its least-known jets, but the program was nonetheless considered a success for Boeing due to its low development costs.

A Boeing 787 Dreamliner flying in the sky.
Photo: vaalaa | Shutterstock

If Boeing wants to continue the 7-7 formula, presently, the only number free is 797 - this model has long been rumored to be a new middle-market plane, but Boeing appears to have put the brakes on any new midsize aircraft design. Should it need another number for a new model, the company could add a fourth number to the mix, as it did with the proposed Boeing 2707 Super Sonic Transport (SST), the plane billed as the United States' answer to Europe's Concorde.

What are your thoughts on why Boeing named the aircraft the 720? Do you feel that this was a good move by the company? Let us know what you think in the comments.

Source: Boeing Frontiers

  • 787-8 Dreamliner
    Boeing
    Stock Code:
    BA
    Date Founded:
    1916-07-15
    CEO:
    Dave Calhoun
    Headquarters Location:
    Chicago, USA
    Key Product Lines:
    Boeing 737, Boeing 747, Boeing 757, Boeing 767, Boeing 777, Boeing 787
    Business Type:
    Planemaker