Regional Express has rejected allegations of unsafe airline practices as "baseless" and "malicious".
Rex have hit back after the Australian Licenced Aircraft Engineers Association reportedly accused them of intimidating staff and bullying them out of reporting serious mechanical issues, and called for its entire fleet to be grounded.
Rex said the accusations were first raised by a "disgruntled engineer" to the Fair Work Commission.
Rex chief operating officer Neville Howell said the accusations were cowardly and the airline was proud of its safety management.
"We believe that our safety culture, as part of the Safety Management System, is second to none," Mr Howell said.
"Realising that these baseless accusations are not getting any traction, some are now taking the despicable and cowardly approach of launching anonymous malicious attacks on Rex in the press.
"Rex will not be making any further comments on this matter and we will leave it to the safety authority to judge if our safety culture is lacking in any manner."
The Civil Aviation Safety Authority confirmed it had received a document earlier in the year from the Australian Licenced Aircraft Engineers Association, which alleged Rex had breached its safety obligations.
"We received all the information from Rex and the union," CASA corporate communications manager Peter Gibson said.
"We're working through it in a timely fashion but, of course, we can't rush it."
Rex currently operates more than 50 aircraft to 60 destinations across regional Australia, with many flights in the North West including Mount Isa, Julia Creek, Richmond, Hughenden, Winton, Birdsville, Bedourie, Boulia, Burketown, Doomadgee, Karumba, Normanton and Mornington Island.
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