The woes of Qantas have worsened after a plane suffered engine trouble and Prime Minister Julia Gillard stepped back from possible government intervention in its union disputes.
Last Friday, Ms Gillard floated the prospect of the government stepping in under the Fair Work Act if the parties could not reach agreement.
On Monday, she urged Qantas management and unions representing ground crew, aircraft engineers and pilots to return to the bargaining table, and settle protracted pay and conditions disputes.
"We are still at the stage in this dispute where both parties say they want to negotiate a conclusion to it," Ms Gillard told ABC Radio in Brisbane.
"So my message has been loud and clear: they should get round a table and get it done."
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The Transport Workers Union (TWU), which represents ground crew workers, supported Ms Gillard's softened stance.
"I'd say this to the prime minister, keep making your calls," TWU national secretary Tony Sheldon told reporters on Monday in Sydney.
"At some point, Qantas will listen because we're prepared to negotiate."
Qantas said it had grounded five of its aircraft from Monday morning because of an ongoing industrial dispute with maintenance engineers.
It cancelled 16 flights on Monday and estimates it will cancel more than 100 flights this week.
The Australian Licenced Aircraft Engineers Association (ALAEA) said Qantas had scheduled months ago to ground the planes.
"We have obtained Qantas' own paperwork which shows that the aircraft they are referring to today were actually slated for disposal back in April, and has absolutely nothing to do with our dispute," ALAEA federal secretary Steve Purvinas said in a statement on Monday.
The ALAEA expects on Thursday to continue its negotiations before Fair Work Australia and last Friday cancelled all planned strike action before the Qantas annual general meeting on October 28.
The Australian and International Pilots Association (AIPA) has ruled out taking strike action, but it has slammed the airline and urged it to return to negotiations.
"(Qantas) are clearly committed to aggravating and exacerbating this dispute and Australians deserve to know why," AIPA president Barry Jackson said in a statement.
Qantas spokeswoman Olivia Wirth said the pilots' claims were unreasonable.
"We simply cannot accept the claim on the table that indicates they want Jetstar and JetConnect pilots to be paid the same wages and conditions as Qantas pilots," she told ABC Radio on Monday.
"We are very much committed to these negotiations, however this one claim makes it very difficult for negotiations to make any headway and make any progress," she said.
There was more negative publicity on Monday after it emerged a Qantas flight from Bangkok to Sydney turned back after passengers heard a bang and the plane vibrated.
The pilot shut down one of the four engines and the plane landed in Bangkok shortly before 11pm (AEDT) on Sunday with no further incident.
Meanwhile, the airline admitted it had lost track of an unaccompanied 11-year-old boy and misplaced the paperwork involving his flight to Hobart.
The boy was wandering around Hobart Airport on his own late at night on September 28, looking for his mother, after getting off a flight from Melbourne, Fairfax newspapers reported.
Qantas said the incident happened during a particularly busy night when the arrivals hall of Hobart Airport was in turmoil because storms in Melbourne had caused flight delays, passenger disruption and lost baggage.
