Rex's run of bad luck has continued with a flight bound for Sydney forced to return to Dubbo after the crew shut down an engine due to a high-temperature reading.
The Regional Express Saab 340 - carrying 23 passengers - made a safe emergency landing after 10am on Thursday.
Civil Aviation Safety Authority spokesman Peter Gibson told AAP the right-hand engine issue was "totally unrelated" to the plane's propeller assembly.
The right-hand propeller of a similar aircraft fell off Regional Express's Albury to Sydney flight last week after the engine was shut down following "abnormal indications".
Mr Gibson said during Thursday's flight the crew "had an indication of high engine temperature on the right-hand engine so it was shut down and they returned to Dubbo".
Regional Express says it's not yet known whether the problem was caused by a "foreign object ingestion" or engine failure.
"(But) whatever the ultimate cause is found to be, the Saab 340 aircraft is designed to climb, cruise and land safely on one engine," a spokeswoman said in a statement.
Rex confirmed "this matter is unrelated to the incident regarding the propeller of flight ZL768" on Friday.
The airline's engineers will inspect the plane and provide a report to CASA.
On Instagram, passenger @devris-hasan posted a video of the right-hand propeller spinning very slowly along with the hashtag #notgood.
Another Rex flight bound for Griffith was forced to return to Sydney Airport on Tuesday afternoon with cabin pressure problems.
Regional Express has a fleet of 55 Saab 340 aircraft and operates about 1500 weekly flights to 58 destinations across Australia.