Except when they buy the wrong configuration, put aircraft on routes the type isn't capable of supporting, wrong engines, wrong certification - all done at various times in the last 15 years. Or even better, lease new aircraft to park them! Expensive and very stupid rookie mistakes that are totally unnecessary!
V-Jet,
Easy too look back at the past and thrown stones,
but remember that aircraft have substantial lead times and market conditions (eg. appropriate config for A380s due to GFC and the like) and delivery times (eg. 787s) or competitor activity (eg. startup of Scoot/AirAsiaX) can quickly change the right answer under long term plans.
Agree the large number of A320s is a potential issue if the Jetstars stop growing but I wouldn't know how easy it is to transfer them between divisions, and in the overall scheme of things (ie the $300m loss) at a rumored 20k/mth its not a massive number even if they sit there for 12 months.
Particularly when you have things like QFF deciding to stop spending $40m on an IT system, that it has already spent over $20m on.