I think it was General Electric in the USA, which more than 100 years ago, came up with the basis for how to operate a "monopoly", without "looking like you are a monopoly", and therefore facing regulation and forced divestitures. The concept was to ensure that in any market where they were approaching monopoly status, and therefore at risk of government intervention, ensure that there were exactly 2 other minor competitors in the market.
The 1st - eeking out a profit, but not enough to warrant their investment in expansion, and encroachment.
The 2nd - borderline basket case, that keeps going but demonstrates to anyone outside the market, there is no potential for any additional new entrants.
If we assume that Qantas risks government intervention and regulation if it goes too far above its two thirds domestic market share, then perhaps Qantas would be quite happy to shed its less valuable price sensitive customers and swap them out for (previous) Virgin's quality oriented customers, who are prepared to pay a premium, and are more valuable to their bottom line?