Armed guards are to be deployed on many flights between Australia and Singapore within days, the Australian Government has said.
Guards would be trained to disarm hijackers
The announcement follows a deal between the government and Australia's national airline, Qantas, to share the costs.
There are also plans to allow Singaporean security officers to guard flights between the two countries.
Singapore is considered to be a prime target for the militant Islamic group in the region, Jemaah Islamiah (JI).
"Agreement was reached this morning (Friday) after long, detailed and times complicated negotiations," Australian Customs Minister Chris Ellison told the Sydney Morning Herald newspaper.
"We want this up and running a-s-a-p (as soon as possible). In fact, we could fly tomorrow," Mr Ellison added.
It is Australia's first agreement on placing air marshals on international flights.
Armed guards have been randomly operating on domestic flights following the 11 September attacks in the United States.
Australia has also been holding talks with America on putting sky marshals on flights there, but Mr Ellison gave no details as to when a deal might be reached.
Both the government and Qantas declined to release details of the cost-sharing arrangements, but experts say the deal will cost up to five million Australian dollars ($5m) a year.
Sky marshals armed with live ammunition and stun guns have been operating on some Singapore Airlines flights since parliament of the city-state passed a law in August.