The industrial dispute at Qantas appears to be getting personal, as Australian Federal Police (AFP) investigate threats made to the airline's chief executive Alan Joyce.

The AFP is investigating specific threats made in letters sent to Mr Joyce and other senior executives.

Mr Joyce says bullying and intimidation of Qantas management is abhorrent and unacceptable and will not force a back-down or change of policy by the airline.

In a memo sent to staff yesterday, Mr Joyce labelled the letters to senior executives "cowardly" and "deplorable" and linked them to unions who are fighting the national carrier's restructuring plans.

Unions which are currently in dispute with Qantas have denied being involved.

Steve Purvinas from the Australian Licensed Aircraft Engineers Association says his union has nothing to do with the threats, and has questioned Mr Joyce's motives for making them public.

"I just think it's a little bit unusual that you would have something in the hands of the police but then you would release those same letters publicly," he said.

"We had a dispute with Qantas three years ago that was quite healthy and there was no signs of this sort of behaviour."

But Mr Joyce has defended his decision to go public.

"For me what's important is that we have to stop the intimidation and the bullying that's taking place in the workplace," he told AM.

"Very clearly, as a consequence of the industrial action that's been taken we've had a number of management and other employees that have experienced destruction to their property, have experienced threats, have experienced letters at home."

"I find it deplorable and wanted to communicate to all 35,000 employees that that was unacceptable, that was something that the company would not tolerate.

"For me the spur on this was the fact that we had other employees around the company being intimidated and bullied and as I said their property attacked, and I just felt that this just got to a level that was unacceptable.

"It took serious consideration before we went public, but they were the main concerns. The safety of my 35,000 employees is my top concern and that outweighs any other considerations.

"We will take this extremely seriously and there will be consequences for anybody caught being involved in this activity," he warned.

"This is nothing to do with PR. This is about some very serious actions that have taken place against a number of our employees.

"I wanted to make sure that that strong warning and that strong information was out there because we have to protect our people."