Southwest mechanics had been complaining about the airline's safety procedures for months before a woman died after being partially sucked through a shattered window, newly surfaced documents have revealed.

In 2017, mechanics at the airline's stations in airports in Dallas and Los Angeles filed whistleblower complaints with the Federal Aviation Association citing their concerns.

They claimed that the airline is so focused on turning flights around quickly that they overlook safety concerns and put pressure on mechanics not to report them and cause problems.

Fourteen mechanics from Southwest's base at LAX (pictured) said there was a cultural problem with reporting safety concerns

The mechanics say they felt pressured to ignore problems or fear losing their jobs.

In neither case was there any evidence that Southwest had violated FAA standards or procedures, but they point to an alarming culture which is also at the root of ongoing union negotiations.

In the LAX complaint, 14 mechanics who were interviewed cited concerns.

The complaint was filed by four of them including Michael Roca who worked for them for three years until he was fired in January.

Michael Roca is one of the mechanics who alleged safety concerns against Southwest Airlines in whistleblower reports in 2017. He was fired in January that year, he claims unfairly

He claims he was made an example of because he had been finding 'too many' things wrong with aircrafts.

Southwest bosses said he was fired for improperly securing an oxygen bottle.

As part of the investigation, the FAA spoke to 16 mechanics based at the airline's LAX hub.

'All of the mechanics interviewed except for two felt pressured and under scrutiny as to whether they were either doing their jobs correctly or if they were finding too many things wrong with the aircraft, i.e. finding discrepancies outside of the scope of the routine inspection,' the FAA inspector wrote in their report.

The mechanics' complaints included that the culture 'has changed from a teamwork approach to scrutiny and threatening' and that mechanics were told not to 'make management look bad' with delays.

Their supervisors disagreed and said the mechanics 'just need to get the work done'.

While no violation was found, the FAA inspector observed a worrying culture.

All of the (16) mechanics except for two felt pressured and under scrutiny as to whether they were doing their jobs correctly or if they were finding too many things wrong with the aircraft October 2017 FAA report into concerns over safety at Southwest Airline's LAX hub

'There is an absence of a "Just Safety Culture". Safety Promotion, a key part of an effective SMS seems to be deficient.

'There seems to lack an environment of trust, effective communication and the willingness for employees to share mistakes, concerns or failures without the fear of threats or reprisal.

'This ultimately leads to a degraded level of safety that the SMS is trying to maintain at the highest possible level.'

Despite their observations, no action was required.

In the Dallas complaint, a violation of FAA standards or procedures was found after five mechanics contacted the agency to report their fears.

That report echoed the other's clams that mechanics were questioned when they raised concerns.

'The motivation behind management questioning AMTs and Inspectors when they discover anything outside the scope of a maintenance task and the subsequent use of formal [disciplinary] fact-finding meetings which management utilizes to formally document an inquiry into airworthiness discrepancies, appears as a tool used to influence a relaxing of standards, to look the other way, or to gain a degree of approval through a leniency of standards.

The motivation behind management questioning mechanics and inspectors when they discover anything outside the scope of a maintenance task appears as a tool used to influence a relaxing of standards, to look the other way September 2017 FAA report into safety procedures at Southwest's hub in Dallas

'The result of this pattern is a capitulation of airworthiness and a culture of fear and retribution....the influence being utilized to pressure technicians and question findings influences the programs and reliability tracking of the aircraft both of which have a negative impact on the overall Continuous Airworthiness Maintenance Program (CAMP),' the report said.

That report cited problems such as damage to an aircraft’s flight control rudder balance weight.

A separate lawsuit against the airline includes a deposition from a supervisor who told an employee that if he was worried about losing his FAA license, he should report damage but that doing so could jeopardise his job with the airline.

Southwest Airlines did not immediately respond to DailyMail.com's inquiries regarding the claims and concerns about its safety culture on Friday.

An NTSB investigator is pictured examining the fan blades of the engine which exploded during a flight on April 17, killing a passenger on board

Union bosses however say it is proof of mounting problems for the company.

'These safety issues are going to continue to stay there, they’re not going to magically disappear Bret Oestreich, president of the Aircraft Mechanics Fraternal Association that represents 2,400 Southwest workers, told NBC Dallas.

'[Workers] just do not trust management,' he added.

The problems were described by Southwest’s Vice President Technical Operations Trevor Stedke in December.

He said: 'We’ve had several examples recently.

'Everything from calls to the FAA in DC, to AD over flies, engine operation. We had a wing that flew around [that] was damaged from an unknown period of time with of course nothing documented.

We had a wing that flew around that was damaged... we've had several dents found to be non-compliant... the list goes on and on about several things that examples of what we're bypassing or policies and procedures Southwest’s Vice President Technical Operations Trevor Stedke in December 2017 in response to the FAA reports

'We’ve been through a dent program. We’ve had several dents found to be non-compliant, re-worked without anything documented in our maintenance systems. Damage events, lockout, carryout.

'And you all know that the list goes on and on about several things that examples of where we’re bypassing or policies and procedures and we have got to get that rectified and cleaned up if we have any hope of getting ETOPS and maintain ETOPS in the futurem.'

On April 17, Jennifer Riordan died after being partially sucked out of a passenger window which was shattered by a piece of shrapnel from an exploding engine at 32,000ft.

What caused the engine to fail and ultimately led to her death remains unclear but it is believed to have been triggered by a loose fan blade which, investigators believe, was compromised by metal fatigue.

Now, engine fan blades are being subjected to a more through scanning process as part of pre-take off safety checks.

The Boeing 737-700 which Riordan was flying on had been checked multiple times in the days before the accident and no problems were found.

In the days immediately after the catastrophe, some speculated if Southwest's notoriously quick turnaround time between flights may have had something to do with the delay.

Business and markets pundits used it to explain why it is a popular investment given the profitability its time in the air vs on the ground track record.

In statement on Friday, an FAA spokesman told DailyMail.com: 'The Federal Aviation Administration investigated the whistleblower complaints against Southwest Airlines and found no substantial violation of Federal Aviation Regulations.

'However, investigators raised concerns that the strained relationship between the company and mechanics might potentially affect safety.

'As a precaution, the FAA assigned additional inspections to monitor the company’s maintenance operations.

'This is standard protocol during contentious labor negotiations and other situations that warrant increased scrutiny.'