Dozens of engineers responsible for regulation of the long-delayed 787 "Dreamliner" aircraft told US authorities that senior Boeing managers pressured them to approve designs and parts before they felt ready.

They said that when they tried to enforce official standards on the 787 programme they came under "undue pressure" and were either "talking to a brick wall" or subjected to "verbal abuse and verbal ridicule".

Documents show that in 2009, Boeing handled 21 "issues" - as the company classified them - where engineers with Federal Aviation Administration (FAA) authority felt they had come under "undue pressure". The papers were obtained by Al Jazeera's Investigative Unit, as part of follow-up research for its documentary Broken Dreams: The Boeing 787 .

A chart from Boeing's records shows it was dealing with two issues every month, except in October 2009 when it dealt with three cases. There were no issues reported in the final two months of the year.

Boeing employed the engineers, but they were also authorised to represent the FAA, which says that since 2008 it has received three formal reports of "undue pressure". The regulator investigated all three reports, but did not substantiate any of them.

Chasing a dream: Timeline of the Boeing 787

In 2010, with the much-hyped 787 "Dreamliner" already years delayed and several billion dollars over budget, a group of four senior regulating engineers reported that they worked in "an atmosphere of undue pressure" at Boeing "driven from second-level management and above".

In a phone conference in April that year, they complained that "workload, performance and expectations relative to schedule" were too high and that they were facing "unprofessional negativity" from their colleagues in "a punitive environment".

I ... was being asked to do something that I absolutely could not do as an [Authorised Representative of the FAA] Engineer responsible for regulating flammability standards of the 787

The group, who regulated the plane's fuel systems, told the FAA that other Boeing engineers portrayed them as "impediments and bottlenecks" to production, who were slowing down production by "nit-picking" in a "contentious and arbitrary" way.

One engineer even said that a Boeing manager introduced him to colleagues as "The Bottleneck". Another reported that a manager had threatened to remove him from the fuel systems team if he continued to make regulatory demands.

'Brick Wall'

One senior engineer complained he was "talking to a brick wall" when insisting to Boeing engineers and managers that regulatory standards should be enforced.

"I ... was being asked to do something that I absolutely could not do as an [Authorised Representative of the FAA]," wrote the engineer, who had responsibility for regulating flammability standards on the 787. "I could not continue the meeting without going beyond unacceptable stress levels, so I walked out."

The FAA hands over responsibility for regulation of aircraft such as the 787 to Boeing engineers, saying they lack the expertise and resources to do it themselves, and that modern airplane programmes are too complicated to regulate independently.

If the FAA-authorised engineers at Boeing then feel they are coming under undue pressure from company managers, they complain to the FAA, which then investigates, consulting Boeing management.

Interview: The former Boeing union president

"I always believe that where there is smoke, there is fire," said former Boeing Engineers Union President Cynthia Cole, after seeing the documents. "I would have expected Boeing Commercial Airplanes (BCA) to bring in a Tiger Team from Boeing Defense to conduct an impartial investigation."

That did not happen. The FAA investigated complaints of undue pressure on the Boeing 787 programme in 2009, 2010 and 2011, but in each case rejected them and took no further action. It has released details of the cases in response to a freedom of information request made by Al Jazeera more than two-and-a-half years ago, as part of the award-winning investigative documentary, Broken Dreams: The Boeing 787.

Al Jazeera is releasing all the documents online here:

<a href="https://www.documentcloud.org/public/search/projectid%3A%2027443-boeing-faa-documents-june-2016%20">View/search document collection</a>

The papers show that in 2011, FAA officials visited Boeing and found managers were "applying pressure to identify changes and minor instead of major" in order to avoid regulatory scrutiny. They also found some suppliers were not delivering parts that complied with drawings.

After its investigations, the FAA wrote to Boeing on June 29 demanding action on six issues and requesting a response within 30 days. Boeing replied on September 8, several weeks past its deadline, stating that no corrective action was needed on any of the six issues. The FAA told Al Jazeera it was "satisfied with Boeing’s investigation and the associated outcomes".

"This seems to fall in line with the new Boeing culture," said Cole, who also said the relationship between Boeing and the FAA "may have become a bit too cozy."

"A bit of an adversarial nature between the FAA and Boeing engineering keeps everyone on their toes," she said.

"If the FAA was acting truly independently, I would have expected the Investigation and Cause Summary to have netted some recommendations for required further actions. 'Good enough' does not work for commercial aircraft safety."

Interview: The fired engineer

The FAA says it works jointly with Boeing toward similar safety objectives. "As a regulatory authority, the FAA also conducts oversight of BCA in accordance with federal law and FAA policy."

After its investigation, the FAA made no recommendations or demands for action, but simply identified and recorded a number of problems at Boeing:

- Managers perceived as "applying pressure" on regulating engineers

- Managers transferring regulating engineers when they were not happy with their demands

- Regulating engineers not being consulted on appeals against compliance rulings

- Management performing tasks meant for regulating engineers

- Concern that "pressure is now being applied" to workers who provide data to the regulating engineers

Boeing says all allegations of "undue pressure" were taken seriously, thoroughly investigated, and found to be "without merit". The company added that it works "appropriately and professionally with all oversight authorities worldwide to ensure our products conform to the highest regulatory and safety standards".