engine bleed air, bypass air

Engine bearing seals are installed to ensure that critical engine bearings are continuously lubricated, and to prevent engine oil from leaking into the compressed air stream. Engine seals will leak a small amount of oil as a function of the seal design. This is known as the permissible oil leak rate.

... Oil leaks may be detected by an odour often called 'dirty socks', or, in more serious cases, by smoke in the cabin. This is known in the industry as a fume event.

Both Airbus and Boeing moved to using electrically powered aircon, for much cleaner air, for their later aircraft.

Undoubtedly Boeing's fault for not having full self flying beta.
https://asn.flightsafety.org/wikibase/476745

Not just Spirit AeroSystems Holdings, Inc. ... https://aviationa2z.com/index.php/2025/03/13/over-500-boeing-787-with-faulty-parts-cleared-audits/

Fraudulently faulty parts made, tick-box certification with no physical checks

Fraudulently faulty parts made, tick-box certification with no physical checks

Isn't the fiduciary duty to the shareholder to make the most money ANY way wonderful?

[...] None of these audits included physical inspection of the floor fittings, which serve as structural elements in the aircraft.[...]

WASHINGTON/SEATTLE, March 14 (Reuters) - U.S. planemaker Boeing(BA.N) lost its way and also lost the trust of the American people after a January 2024 mid-air emergency involving a new Boeing 737 MAX and two fatal crashes in 2018 and 2019, Transportation Secretary Sean Duffy said Friday.

Duffy also said the Federal Aviation Administration is not yet ready to lift a 38-plane per month production cap on the 737 MAX.

"When you breach the trust of the American people with that safety and with your manufacturing, we're going to put the screws to you to make sure you change your ways and start doing things right," Duffy told Fox News Channel’s The Faulkner Focus after a visit on Thursday to the Boeing 737 factory in Renton, Washington. "They've lost trust."

More than six months later, the future of Starliner is unclear. During the post-splashdown news conference for Crew-9, the manager of NASA's commercial crew program, Steve Stich, said that Boeing's new CEO, Kelly Ortberg, remained "committed to Starliner." However, longstanding problems dog the project.

Boeing has incurred enormous losses due to Starliner's difficulties. As of February's financial results, the company has bled over $2 billion, which is unlikely to stop until the spacecraft finally becomes operational.
...

Thus there is a real chance that Boeing might throw in the towel in the coming months and extract itself from an increasingly expensive contract. Unlike with its Space Launch System work, the aerospace giant is on the hook for the ballooning Starliner costs.