Jetstar flight delays

[Tim B]

A friend was travelling from the Sunshine Coast to Melbourne (Tullamarine) recently, and after many bad experiences with Jetstar decided to travel with Virgin.
Lucky for him as the Jetstar flight leaving on the same route and around 15minutes later was delayed indefinitely due to "Operational Requirements".
Does this mean something like the flight crew had exceeded their hours, and the plane had to wait for replacement crew, or something similar?