Sebastian Vettel set a searing pace in the final practice session ahead of qualifying.
Virgin and HRT are at risk of not starting the Australian Grand Prix.
Jenson Button was fastest in second practice.
Red Bull and Ferrari were closely-matched over longer runs in first practice.
Mark Webber set the fastest time in the dying moments of the first practice session in Melbourne.
One driver on the 2011 grid has been waiting more than a decade for a win.
Virgin sign Jerome d’Ambrosio to partner Timo Glock in 2011.