Let's move back to 2008, when Boeing announced the delayed delivery of the 787 Dreamliner, it revealed that at least 8,000 fasteners must be replaced on each of the top 10 787 planes being assembled because of installation problems. Most of these fasteners are bolts and nuts.

The faulty fasteners are used inside the fuselage to fix the titanium alloy structure on carbon fiber composites. During the pressurization test of a completed 787 airliner, it was found that there were small and unacceptable gaps in the head area of thousands of fasteners in the fuselage.

After Boeing's preliminary investigation and analysis, these problems only appear in the internal structure of the fuselage shell, such as the floor grille. First of all, this will not be a security threat, but because the existence of gaps will reduce the durability of the fuselage, so decided to replace all the faulty fasteners.

According to people familiar with the plan, nearly 2,500 to 5,000 fasteners need to be replaced for each aircraft or seat gasket. Boeing has publicly stated that it is estimated that nearly 3% of installed fasteners need to be removed and re-installed.

Boeing stressed: "The problem is the installation of fasteners, not the fasteners themselves."

The senior engineers in charge of the project are making every effort to solve the problems existing in the installation of Boeing aircraft fasteners and its supporting structural equipment as soon as possible.

The difficulty of this project is how to remove fasteners and reinstall them at the same time, but also to avoid possible damage to composite materials.

A senior engineer said: "The risk involved is that some fastener drilling must be increased. This is a common practice in the process of production and maintenance.

"Fastening structures are designed for future reusability, mainly for maintenance in use."

When Boeing first demonstrated Dreamliner One in July 2007, they replaced temporary fasteners with long-term fasteners, causing damage. Now Boeing is facing a time-consuming repair of Dreamliner One.

Boeing is retraining all 787 mechanics at the Everett plant for new fastener installation procedures. People familiar with the matter pointed out that the incident was another measure to delay the resumption of workers after the strike of the International Association of Mechanics. According to the strike resolution, the mechanics will not resume work until November 10. Only the mechanic who has completed the retraining can continue to work on the plane.

Some people familiar with the fastener market told Flight Blogger that the problem originated from installing two different types of fasteners in four flight and two ground test aircraft, as well as more than a dozen currently available seat gaskets.

The first problem arises from drilling holes used to adsorb titanium and carbon fibers. When the hole is drilled into titanium, the burr usually remains on the left edge of the hole. Due to the special strength of titanium, when a fastener is mounted in the hole, the head will stay on the burr without tightly bonding with the surface.

As the head of the fastener stays on the burr, the load will be distributed on a point rather than on the surface equally. In addition, in the worst case, if the asymmetric high shear load occurs, the high strength titanium burr will destroy the integrity of the fastener structure. Titanium is used in key structural parts of aircraft, such as fuselage and water stabilizer connections.

It is reported that the fastener problem was first found on the engine hanger during the static test of the body. All of the Averite planes dismantled the racks and recalled them to Spirit Aero Systems in Wichita, Kansas, which is the world's largest independent supplier of spare parts for civil aircraft.