A Virgin Australia flight operations engineer who raised safety concerns with his superiors was sacked for alleged misconduct, documents show.

Internal records show Brisbane-based Virgin employee Yahya Khattabi raised concerns in mid-September about the training manuals given to the airline’s new Boeing 737 pilots, alleging they failed to comply with federal regulations.

Senior management disagreed with his claims, but Khattabi persisted and organised a meeting with his superiors for further discussion on 21 September. The meeting did not take place.

On the same day, Khattabi received a letter telling him he was suspended with immediate effect for serious allegations that he had breached Virgin’s code of conduct.

The airline wrote to Khattabi again five days later, expanding on its reasons for the suspension. It alleged Khattabi had “sent a series of emails” in the week before his suspension that “included content and/or adopted a tone that was threatening, inappropriate, disrespectful and unprofessional”.

It also cited Khattabi’s reaction to being suspended as evidence of his misconduct.

Khattabi, the airline said, had torn up the suspension letter, laughed, called his superiors “robots”, roughly pulled notes from a senior executive in the room, and threatened to sue the individuals present.

Virgin terminated his employment several weeks later, saying it had lost trust in him and that he had previously been warned about his communication style.

In its termination letter, Virgin said the way he had raised the safety concerns was threatening and disrespectful.

“Further, your insistence in your response that raising safety concerns and addressing those concerns was a part of your job indicates that you fail to appreciate that while you may be required to raise and deal with such concerns, the manner in which you raised and pursued those concerns was inappropriate, threatening, disrespectful and unprofessional and ultimately a breach of the code of conduct and your employment contract,” the airline said in its termination letter to Khattabi.

Khattabi denied he had acted in a threatening or disrespectful way, but asked colleagues who were offended to “accept my apology as it was never my intention”.

He has since lodged an unfair dismissal claim in the Fair Work Commission, which is due for a conciliation hearing on 22 November, according to documents filed with the tribunal.

Khattabi has also composed a 43-page report detailing his concerns with Virgin’s 737 training material and submitted it to the Civil Aviation Safety Authority (Casa).

“What I found was astonishing, the line pilots were left with very little technical knowledge on takeoff and landing performance,” his report to Casa said. “The course itself was confusing with substantial inaccuracies and outright incorrect information.

“After careful investigation, I found out that these were not just inaccuracies, but breaches to Casa regulations including the CAO 20.7.1B and CAR 217.”

His report linked the failings to “poor landing performance in Christchurch in 2015 and a runway excursion in Hobart in 2010”.

“Both incidents involve the B737 flight crew and both incidents are due to similar causes, mainly, the inadequate training of the B737 flight crew on aircraft performance,” he said.

Guardian Australia understands Casa has received the report only recently but is considering the information. No formal investigation has begun.

In a statement, Virgin Australia said it conducted its own audit of Khattabi’s “regulatory compliance” concerns.

“We acknowledge concerns were raised by a former employee about regulatory compliance however an audit of the applicable procedures found absolutely no truth to these concerns and the matters to be compliant,” a spokeswoman said.

She said safety was “at the forefront of Virgin Australia’s operations” and was its number one priority.

“Virgin Australia is fully compliant with all Casa regulations and has not been informed of any investigation into regulatory compliance matters,” she said.

The airline could not comment on the specifics of Khattabi’s unfair dismissal claim.

Aviation expert Neil Hansford, who runs the consultancy Strategic Aviation Solutions, reviewed Khattabi’s complaint after being approached by Guardian Australia.

Hansford said his early reading suggested the complaint was worthy of investigation.

“These manuals in the main are used by people who are joining Virgin to fly the 737,” he said.

“They’re pretty important documents. Without doing an analysis of his documents [myself], they appear to raise issues that are worthy of more attention than what they appear to have had at Virgin.”

Last month, while Khattabi was suspended, Virgin’s group executive, Rob Sharp, wrote to tell him his safety concerns were being investigated, or had already been investigated.

“I am the [air operator’s certificate] holder and I am fully aware of your specific safety-related concerns and these concerns have been or are in the process of being investigated,” Sharp told Khattabi.

“You were also advised that some of the issues you have raised have already been dealt with. To the extent that your email below raises any issues not raised before, these will also be reviewed.”

• This reporting is supported by the Susan McKinnon Foundation through the Guardian Civic Journalism Trust