One of the final parts of the production process of large airliners is painting. All airlines feature carefully-designed liveries to best reflect their brand image, and this is first applied to an airliner after assembly is completed, and before delivery. You’d think that before being painted, the aircraft would simply display bare metal, as seen on the former American Airlines livery, for example. In reality, unpainted Boeing airliners feature a glossy emerald green color during the assembly process, a striking and unusual color scheme.

Most modern airliners are primarily constructed out of an aluminum alloy, and the green color is a coat of primer paint. The primer is applied during the production of various aircraft components, which are then shipped to final assembly still wearing this green color. Boeing airliners are then assembled and occasionally even perform flight tests while painted green, before receiving their interiors as well as their full airline livery. The aircraft completes more ground and flight tests before being handed off to the customer.

The Process Of Building An Airliner

Individual components of an aircraft are constructed worldwide by various suppliers and contractors. The degree to which component assembly is outsourced varies by aircraft; the Boeing 737’s fuselage is assembled in Wichita, Kansas, by Spirit AeroSystems (formerly and soon to be operated by Boeing), while the 777’s fuselage is assembled by Boeing in Everett, Washington. As a whole, Boeing traditionally assembles most aircraft components in-house, with the 787 featuring by far the highest level of outsourcing.

The final assembly line for the Boeing 737 is located in Renton, Washington, while the 767 and 777 are completed in Everett. The 707, 727, and 757 were assembled in Renton, while the 747 was formerly built in Everett. The Boeing 787, meanwhile, formerly had a final assembly line in Everett, but this line was shut down in 2021 as Boeing consolidated 787 production in North Charleston, South Carolina.

Once the fuselage is completed and placed on the final assembly line, the interior systems, such as electrics, plumbing, and hydraulics, are installed. Workers then attach the radome and doors before attaching the aircraft’s wings. From there, the aircraft’s landing gear is installed, followed by the vertical and horizontal stabilizers. After this, the engines are installed, and finally, the aircraft’s interior can be installed before it’s sent to the paint shop. Overall, a Boeing 737 MAX can be assembled in roughly nine to 10 days, while a widebody Boeing 777 can take roughly 17 days to assemble.

Why Are Newly Constructed Boeing Airliners Green

The green paint is a primer intended to preserve the aluminum alloy used for the aircraft’s components. While the alloys used are incredibly durable and resistant to corrosion, the primer adds an extra layer of protection against corrosion and metal fatigue. The paint itself is actually yellow in color, but lampblack is added to the paint to protect against ultraviolet light rays from the sun. The addition of lampblack alters the shade of the primer from yellow to green.

The anti-corrosion primer is a zinc-chromate coating, which was pioneered in the automotive industry by Ford in the 1920s. While it was first used in car assembly, zinc-chromate primers are most heavily used in the aviation industry today for aluminum protection during production, and they have become the standard across all manufacturers. You will, however, notice that some components of a Boeing airliner under production feature mismatched shades of paint. This varies from aircraft type, but it is typically the result of different primer brands being used by various suppliers.

Zinc-chromate primers are specifically used to protect aluminum alloys from corrosion and fatigue, which is why they’re only applied to certain sections of an airliner. The Boeing 787, for instance, is primarily made out of carbon composite materials, which generally do not experience corrosion. As such, you’ll never find a 787 wearing the green primer coating. In addition, certain sections of an aircraft, such as the wings of a Boeing 747-8, may be constructed out of carbon composites and therefore do not require the primer.

Painting An Airliner After Final Assembly

After being fully assembled, it’s time for the aircraft to receive its livery. Boeing operates its own painting facilities in Renton, Everett, and North Charleston. Due to capacity constraints, you may occasionally see aircraft flying to another paint facility rather than the one at its production site. Furthermore, an airline may opt to have an aircraft be painted at a contract facility after assembly rather than by Boeing. This was the case with Alaska Airlines’ newest Boeing 787-9, N784HA, which was painted by International Aerospace Coatings in Fort Worth, Texas.

It can typically take around a week to repaint a narrowbody airliner like the Boeing 737, while a larger widebody like the 777 may take multiple weeks to be painted. While repainting an aircraft involves stripping the existing paint off the aircraft, in this case, the primer helps bind the new paint to the aircraft’s structure. The windows, engine intakes, and sensitive equipment are covered up before a base coat of paint is applied. From there, the airline’s livery design and logo are painted, then finally, a clear coat is applied.

Aircraft are typically repainted every six to ten years, and repainting involves stripping an aircraft down to reveal the bare metal. This is mainly done to save weight, since paint on an airliner can weigh hundreds of pounds. The preexisting primer is also removed and replaced before the new coats of paint are applied. It can routinely cost over $100,000 to repaint even a smaller narrowbody like a Boeing 737, while a widebody such as the Boeing 777 can cost double and require several weeks to be repainted.

How Does This Differ From Carbon Composite Airliners

You’ll never see a Boeing 787 Dreamliner wear the bright green colors because it’s made out of carbon-composite materials. As such, it does not require the same zinc-chromate primer that other Boeing airliners wear. However, the 787 still requires primer paint. Mainly, the carbon-composites used on the 787 require a specialized primer to help bond the paint to the fuselage. With the 787, the components are often painted before being placed for final assembly, but the primer is still present underneath the skin.

The difference between the Boeing 787 and other Boeing aircraft is simply that the Dreamliner uses a different primer, and the paint procedures during assembly differ. However, with the 787, Boeing also sought to radically alter its production and assembly process. Perhaps most notably, the 787’s fuselage is made out of whole barrels rather than in traditional panels. Although Boeing has had some issues with the 787’s assembly process, the barrel process is meant to be cheaper with fewer parts than the panel process.

The 787 features significantly more outsourcing than prior Boeing airliners. For older projects like the 777, many components were manufactured in-house close to the final assembly line. With the 787, Boeing has delegated the manufacturing of most of the aircraft to suppliers. These components, such as the wings and fuselage barrels, are then transported to the final assembly line. Boeing then assumes the responsibility of attaching all of the components and installing the aircraft’s interior before delivering it to the customer.

Differences With Airbus’s Procedures

Just like Boeing, Airbus uses primers on its aluminum aircraft to protect against corrosion, as do all manufacturers, and Airbus’s primer paint also has a green color. Airbus’s primers have a matte appearance as opposed to the glossy look of the primers used on Boeing aircraft, but this is only due to a difference in the brand of primer used. You’ll also notice similar matte primers being used by Gulfstream. The primer paint used by Bombardier for its business jets, meanwhile, is closer to yellow.

The Airbus A350 is a composite airliner just like the Boeing 787, meaning that it doesn’t require the same type of primer as the company’s metal aircraft types. However, Airbus still uses a different type of primer with a prominent yellow shade, which is easily spotted when A350s are towed between various Airbus plants. In addition, Airbus routinely performs test flights with unpainted A350s before they receive their customer’s livery, and has even flown unpainted from Toulouse to the Airbus Tianjin Widebody Completion and Delivery Center in China.

Airbus’s production and assembly methods differ significantly from Boeing’s. As another example, the A350 is built using traditional fuselage panels rather than the barrel method used by the 787, despite being a new airliner. The two aircraft also feature significant design differences. As a whole, however, the two companies both achieve the same result, in that their airliners are exceptionally durable, reliable, and perform well for their customers, ensuring that future orders will keep coming in for these two proven manufacturers.