A whistleblower claims that Boeings’ 787 Dreamliner could be left without oxygen if the cabin were to suffer a sudden decompression.

Emergency oxygen systems are supposed to keep passengers and crew alive if the cabin pressurisation fails. Without this system, passengers could be incapacitated, fall unconscious, or even sustain brain damage and/or die.

John Barnett is a former quality control engineer who has worked for the company for 32 years, including in the South Carolina plant where the 787 Dreamliner is manufactured.

“Boeing South Carolina is strictly driven by schedule and cost,” Barnett claims, suggesting that up to a quarter of the oxygen systems could be faulty but were deliberately fitted to planes to save on costs.

Barnett discovered the fault in 2015. He claims that under-pressure workers even fitted sub-standard parts from scrap bins to aircraft on the production line and- in one case – with the knowledge of a senior manager.

Boeing denies the allegations of cost-saving at the expense of security. But Barnett is taking legal action against Boeing for denigrating his character and forcing him to retire.

Boeing denies forcing Barnett to retire and argues that it has created a culture that encourages employees to raise concerns and rigorous processes to ensure they are listened to.

Last week Boeing was forced to ground 50 of its popular 737NG planes due to cracks on the haul. Among the worst affected companies are Australia’s Qantas and Ireland’s Ryanair. The firm has also come under intense scrutiny following the Ethiopian Airlines 737 Max crash in March.

The view that Boeing prioritized cost-saving over security is echoed by former engineer Adam Dickson, who was involved with the development of the 737 Max at Boeing’s Renton factory in Washington state. He told the BBC that his team had to fight the factory and management to maintain process and quality to standard.