After a 737 Max 9 door panel blew off during an early January Alaska Airlines flight, an investigation initiated by the air safety regulator found that Boeing used Dawn liquid detergent as a lubricant for the 737 door seal.

According to a slide presentation seen by The New York Times, the Federal Aviation Administration discovered hundreds of issues with Boeing and one of its major suppliers’ manufacturing processes during a six-week audit of the aircraft manufacturer’s 737 Max production.

The examination was started by the air safety regulator after a 737 Max 9 door panel blew off during an early January Alaska Airlines flight. The government revealed last week that, although it did not offer details, the audit had discovered “multiple instances” in which Spirit AeroSystems, the supplier, and Boeing had violated quality-control regulations.

Boeing whistleblower John Barnett was discovered dead in Charleston, South Carolina, where he was supposed to undergo the third day of his AIR21 case deposition.

Despite being extremely technical, the presentation that The Times studied provides a more thorough overview of the findings of the audit. Boeing’s quality-control procedures have been the subject of intense scrutiny since the Alaska Airlines incident, and the results add to the body of information regarding the company’s manufacturing errors.

The F.A.A. carried out 89 product audits—a kind of evaluation that looks at various areas of the production process—for the section of the investigation that was centered on Boeing. The presentation stated that the aircraft manufacturer had 97 instances of alleged noncompliance, passing 56 audits and failing 33.

For the portion of the investigation that was centered on Spirit AeroSystems, the company that manufactures the fuselage, or body, of the 737 Max, the F.A.A. also carried out 13 product audits. According to the presentation, six of those audits produced passing marks and seven produced failing ones.

A document outlining some of the examination’s findings states that the air safety agency saw Spirit mechanics using a hotel key card to verify a door seal at one point. The paper stated that the action was “not identified/documented/called out in the production order.”

In another case, the paper states that the F.A.A. observed Spirit mechanics using liquid Dawn soap “as a lubricant in the fit-up process” on a door seal. The report noted that the instructions were “vague and unclear on what specifications/actions are to be followed or recorded by the mechanic” and that the door seal was subsequently wiped using a damp cheesecloth.

When asked if using a hotel key card or Dawn soap in those circumstances was appropriate, Spirit’s Joe Buccino responded that the business was “reviewing all identified nonconformities for corrective action.”

Boeing is still “implementing immediate changes and developing a comprehensive action plan to strengthen safety and quality, and build the confidence of our customers and their passengers,” according to Jessica Kowal, a spokesperson for the company.

The F.A.A. gave the business ninety days at the end of February to create a plan for enhancing quality control. Dave Calhoun, the company’s CEO, responded by saying, in part, “We have a clear picture of what needs to be done,” citing the audit findings.

This month, Boeing said that it was in talks to buy Spirit, the company it spun out in 2005. On Monday, Mr. Buccino announced that Spirit had received the F.A.A.’s preliminary audit results and that the company intended to collaborate with Boeing to resolve the regulator’s concerns. He stated that Spirit aimed to eliminate all flaws and mistakes inside its operations.

“Meanwhile, we continue multiple efforts undertaken to improve our safety and quality programs,” Mr. Buccino said. “These improvements focus on human factors and other steps to minimize nonconformities.”

The F.A.A. stated that due to its ongoing investigation into Boeing in response to the Alaska Airlines incident, it was unable to disclose specifics of the audit. The Justice Department has launched a criminal investigation, and the National Transportation Safety Board is looking into what caused the door panel to blow off the aircraft in addition to that inquiry.

According to the slide presentation, the F.A.A. sent as many as 20 auditors to Boeing and about six to Spirit during the investigation. Spirit constructs the fuselage of the aircraft at its facility in Wichita, Kansas, while Boeing assembles the 737 Max at its facility in Renton, Washington.

The audit conducted by Boeing was extensive, encompassing numerous components of the 737 Max, such as its wings and various other systems.

According to the presentation, many of the issues discovered by the auditors were related to not adhering to an “approved manufacturing process, procedure, or instruction.” Other concerns were documentation related to quality control.

“It wasn’t just paperwork issues, and sometimes it’s the order that work is done,” Mike Whitaker, the F.A.A. administrator, said at a news conference on Monday. “Sometimes it’s tool management — it sounds kind of pedestrian, but it’s really important in a factory that you have a way of tracking tools effectively so that you have the right tool and you know you didn’t leave it behind. So it’s really plant floor hygiene if you will, and a variety of issues of that nature.”

One audit focused on the door plug, which is the component that caused the Alaska Airlines jet to blow up. The presentation stated that Boeing did not pass that inspection. Although the precise results were not disclosed in the presentation, the audit raised several concerns about inspection and quality-control paperwork.

The level of employee comprehension of Boeing’s quality-control procedures was also investigated by the FAA. Six corporate engineers were interviewed by the agency, and after grading their answers, the average score was only 58 percent.

Five issues were discovered during a Spirit audit that concentrated on the door plug component. Boeing “failed to provide evidence of approval of minor design change under a method acceptable to the F.A.A.” was listed as one of those issues in the presentation. The presentation did not make it apparent what the design change was.

One of the audits that Spirit failed was the one that concerned installing the door plug. The corporation “failed to determine the knowledge necessary for the operation of its processes,” according to the audit, which also raised questions about the Spirit technicians who performed the job.

Spirit also failed two other audits: one on the installation of cockpit windows and the other on a cargo door.”