The carrier issued a statement on Friday afternoon saying it will reduce the number of services between Sydney and NSW towns Albury, Coffs Harbour, Griffith, Narrandera, Orange, Parkes and Port Macquarie from October 30.
It is also temporarily suspending flights between Sydney and Armidale and withdrawing its far north Queensland route between Cairns and Bamaga.
"The airline is forced to make further reductions to its regional network as the major carriers, particularly the Qantas Group, continued their relentless pillaging of Rex's pilot group," a company statement said.
Qantas has rejected Rex's claims, a spokeswoman told AAP.
In April, Rex reduced or changed flight times for nine services across four states, including routes between Sydney and Broken Hill, Melbourne and Wagga Wagga, and Adelaide and Port Lincoln.
If the workforce situation improves, the reduced services will return to normal operation by the end of March next year.
Rex's April announcement made no mention of its competitors, instead saying there was a chronic shortage of staff and supply chain disruptions.
The affected routes require SAAB 340 twin-engine pilots, who were in heated pay negotiations with the airline in June last year.
Pilots took protected industrial action, including a ban on topping up planes with extra fuel, after extended wage negotiations.
At the time Rex was offering a 5.1 per cent increase, plus catch-up payments, which the Australian Federation of Air Pilots said amounted to a pay cut as it did not cover inflation.
Rex's deputy chairman John Sharp said the negotiations exposed the "hypocrisy" of the union because it agreed to a two per cent pay rise for QantasLink pilots in 2021 and 2022.
The majority of Rex twin-engine pilots agreed to a new pay deal in November.
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