"...unless you are part of the British Commonwealth, it's very hard to work in Australia"
Not so, although being a natural English speaker is an advantage in passing the IELTS test.
Hello, is it possible to be hired by an australian airline without being citizens?
Yes, but you must hold a valid Australian Visa that permits you to work in Australia. To obtain that in general terms you would require employer sponsorship.
"....is possible only getting a temporary visa for working. Is that correct?"
No, not correct. There are various Visas available, both temporary Visas (up to four years) and permanent residence Visas.
You need to check the Australian "Skills in Demand" to see whether your skills are being sought overseas. If your skill or trade isn't on the list, forget it!
If you are thinking of pilot employment, don't get your hopes up as you would need extensive experience, including experience and/or specialist qualifications not readily available in Australia.
We have more than enough young, qualified Australian pilots trying to find flying jobs, without employing low time overseas pilots.