once [Ansett] folded there was only one place to work as a group 20 engineer and that was Qantas.where they had a monoply on the trade in this country(where if you didn't work for them,you didn't work).
Your logic is incorrect. Firstly, it's factually incorrect that QANTAS had a monopsony over aircraft engineers in this country. Then or now.
Additionally to insist that all levels of employment in all industries in one country must only grow or their number remain static is illogical. If that were the case the steam train drivers union would be alive and thriving. Whilst I admit we are talking about unemployment due to different reasons the analogy is still valid.
At that time (ANSETT) some aircraft engineers began employment with Virgin Blue. Not long after some lost employment with Ansett. So two airlines existed still, and they were not the only employer of aircraft engineers (especially in the globe)
The union was looking at bring up the wages to a parity equal to most western countries for aircraft engineers
Why should the wages be at parity globally (or in the Western World) when in each country, each business has it's own fuel costs, tax regimes to comply with, statutory compliance costs, trade barriers, subsidies (government owned airlines), costs of living, supply of labour etc. Why should wages be at parity? Petrol in the middle east costs but a fraction of what it does here, should a union or government body insist on price parity for petrol?
If you want wage parity then you should advocate free migration for skilled labour, of course that won't work in a world where union's can shut a company down for hiring people for the wage they are actually willing to work for.