Look at the age demographic. Lots of young Captains in Virgin and Jetstar. Qantas has a much older average, even many First Officers will leave in the next ten years or so. About half the FOs I fly with are in their 50s.
Qantas Management always stuff up numbers in a cyclical way. Plenty are getting close to running out of hours, all leave gone etc.
This is likely to be a large recruitment, more 787s will be ordered eventually but over 100 new Pilots are needed for the current fleet without allowing for second officers on the 787.
I would think anyone in their 20s or 30s would do well to apply, I for one will be retiring early in a few years.
