SYDNEY: Qantas Airways' chief executive on Saturday said two senior employees prevented from leaving Vietnam over fuel-hedging losses had done nothing wrong, and expressed hope for a quick resolution of the case.

Alan Joyce admitted major losses at budget carrier Jetstar Pacific, part-owned by Qantas and the Vietnamese government but said these were not uncommon among airlines hit by wildly fluctuating fuel prices.

Jetstar Pacific chief operating officer Daniela Marsilli and chief financial officer Tristan Freeman were prevented from returning to Australia on December 19, while state media said its Vietnamese ex-chief executive was arrested.

"The losses that were incurred were a part of global business risk," Joyce told reporters.

"We are, obviously, concerned. We are concerned about the wellbeing of our people. That's the top priority for us. We are working very closely with the authorities," he added.

"We don't have an indication of how long this will take. We, obviously, want it resolved as fast as possible."

Deputy Prime Minister Julia Gillard said Australia was providing assistance through its embassy in Vietnam.

"We are providing consular assistance, doing everything we can trying to get to the bottom of the reason for their detention," she told the Nine Network.

Jetstar Pacific's losses reached a record 546 billion dong (now more than 29 million dollars) in 2008, the year in which former chief executive Luong Hoai Nam earned 2.2 billion dong in salary, the VietnamNet news website reported.

It said the state audit agency concluded there was a lack of management supervision of efforts to hedge petrol costs at the airline.

Qantas spokeswoman Olivia Wirth earlier said its two employees had not been formally detained but are unable to leave the country as they are "working with Vietnamese authorities on an investigation" into fuel-hedging at Jetstar Pacific.

Qantas bought 18 percent of Pacific Airlines in 2008 and turned it into low-cost carrier Jetstar Pacific, later increasing its stake to 27 percent. Vietnam's government is the largest shareholder.

Fuel hedging is common among airlines seeking to lock in the lowest future prices for fuel. But carriers have lost millions in recent years thanks to rollercoaster global oil prices.