Qantas's chief executive said on Monday that the airline's A380 superjumbos will remain out of action for at least the next 72 hours, following last week's scare en route from Singaport to Sydney.
Joyce says oil leaks have been discovered in three engines, on three different aircraft.
He says the leaks are beyond the normal tolerable level, and the engines will bereplaced.
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Qantas has six Airbus A380s, the first of which was delivered in 2007.
The fleet has been grounded since Thursday when QF32 travelling to Sydney from Singapore was forced to turn back after a mid-air explosion of one of the aircraft's four Trent 900 Rolls Royce engines.
The explosion showered debris over the Indonesia island of Batam, while other debris flew up and damaged the wing.
Mr Joyce said it was still "too early" to say what the grounding would cost the airline, which has had to replace flights on routes from Australia to London and Los Angeles and put displaced passengers up in hotels.
He said the focus was still on finding out what caused the explosion on QF32.
Teams of engineers are conducting engine tests on the A380s, alongside crews from Airbus and Qantas.
