A Qantas jumbo jet on its way to Argentina was forced to return to Sydney after smoke was released into the cockpit.
Qantas attributed the smoke to a problem with the aircraft's electrical system, with an airline spokeswoman describing it as a "minimal amount".
Flight QF17, a Boeing 747 jet, landed safely at Sydney Airport at 1.20pm (AEDT) on Monday, about two hours after it departed for Buenos Aires with 199 passengers on board.
Qantas said reports that the Boeing 747 lost pressure in the main cabin were incorrect, adding that oxygen supply to the cabin was unaffected.
The airline organised a replacement flight from Sydney to Argentina which was due to leave early on Monday evening.
The incident was reported to the Civil Aviation Safety Authority and the Air Transport Safety Bureau.
"Our engineers are still working to establish the cause of the issue," a Qantas spokesman told AAP.
The plane was also carrying three flight crew and 18 cabin crew.
The carrier said its flight crew operating the service acted appropriately in line with their training.
The incident comes after a domestic flight from Perth to Melbourne on Friday had to return after flight crew became aware of a vibration in the one engine of the Boeing 767.
Carrying 234 passengers, QF768 returned safely to Perth airport.
Earlier this month, Qantas grounded its flagship Airbus A380 long range aircraft after the an engine on flight QF32 flight from Singapore to Sydney exploded.
The jet returned to Singapore no one on board was injured.
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http://au.news.yahoo.com/a/-/mp/8321620/qantas-reschedules-flight-to-argentina/)