Qantas A380 jets will remain grounded for days after engine oil was found "where oil shouldn't be", the airline's boss says.
Emergency checks found "anomalies" on three of the fleet's new Rolls-Royce engines, chief executive Alan Joyce said.
He told ABC radio it should be days and not weeks before the aircraft were declared ready for fly again.
"On three of the engines what we have found is slight anomalies. Oil where oil shouldn't be on the engines and we are just trying to check, what the cause of that could be," Mr Joyce said on today.
"These are new engines on new aircraft, they shouldn't have these issues at this stage so it's given us an indication of an area for us to focus into.
"It's too early for us to say what components or parts of the engine we think could have been the issue."
Eight hours of checks have been carried out on each of the A380 engines since the airline was plunged into crisis by a mid-air explosion over the Indonesian island of Batam.
Asked what the problems were, Mr Joyce said: "We're keeping an open mind on it but given that these engines are new, these engines have been maintained by Rolls-Royce ... and looking at what we've seen occur on this engine, we think it could have been a materials issue on the engine or a design issue on the engine.
"This has happened before on other engines around the world. There have been in-flight shut downs on other engines and usually the manufacturer can make recommendations about what needs to be modified and changed in order for the engines to be serviceable again."
Rolls-Royce was also investigating the fault, Mr Joyce said.
"On three of the engines we did find issues that were being investigated further. That has involved changes to engines on aircraft and those engines are going to be looked at further by Rolls-Royce and their own engineers.
"That testing is still continuing, the dialogue with Rolls-Royce, Airbus and CASA, the regulator, is continuing today and hopefully over the next day or so we'll have an understanding of when the aircraft can get back in the air.
"Our top priority is making sure we have the continued safe operation of the aircraft and if this takes a bit longer we are going to give it as much time as possible to ensure that we are comfortable with the safe operation of the aircraft."
The airline has suffered two safety scares over the past week.
As well as the mid-air explosion of the A380 engine on Thursday, Qantas suffered another setback when a Boeing 747-400 en route to Sydney on Friday was forced to turn back to Singapore 20 minutes after take-off because of a problem with one of its engines.