Regulators in Canada and New Zealand announced they would move to the so-called "rule of two" within 24 hours of the news last week that the Germanwings first officer had apparently locked out the captain before plunging the plane into the French Alps. The European Aviation Safety Agency also recommended at least two people be present in the cockpit at all times.

US airlines had already had the "rule of two" in place before the Germanwings crash. It means that, if one pilot needs to exit the cockpit to use the toilet, a flight attendant will enter the cockpit until the pilot returns.

Minister for Infrastructure and Regional Development Warren Truss said the new rules would take effect immediately and will apply to all domestic and international flights by Australian operators, including Qantas, Jetstar, Virgin Australia and Tigerair Australia which operate aircraft with more than two flight attendants. He said that covered all aircraft with 50 or more seats, and so included some larger regional turboprops as well as jets. 

"We would expect to see this policy in place within hours on our major airlines," he said.

It is understood Qantas chief executive Alan Joyce and Virgin chief executive John Borghetti were advised of the changes during a conference call with Mr Truss on Monday.

The arrangements will be reviewed after 12 months to determine their effectiveness. "We will be monitoring this new imitative to make sure it is appropriate or for that matter that it does not create new risks that have to be addressed in other ways," Mr Truss said, after noting on Friday that flight attendants are not subject to mental health checks as thorough as those conducted on pilots.

Mr Truss said as the investigation into the Germanwings crash continued, the Australian government aviation agencies would continue to work with airlines to identify further improvements to the safety and security of cockpits.

"This will include Australian airlines, flight crew associations and the Civil Aviation Safety Authority working together to review the requirements for medical testing, including mental health, of flight crew members," he said.

Airline pilots under 40 are subject to annual medical exams and those over 40 receive medical exams every six months to ensure they remain in a fit physical and mental state to fly.

Germanwings First Officer Andreas Lubitz, who is accused of crashing the plane, had previously been treated for depression, according to news reports.

Australian pilots with depression are allowed to fly after a period of being grounded for treatment, provided they are treated with a select list of medications.

Mr Truss said Australian airlines took the health and medical condition of their pilots "very seriously".

"There are procedures the airlines have which rely on the observations of pilots and anyone demonstrating any erratic behaviour or concerns about their medical health are immediately assessed to ensure they are able to operate the aircraft," he said.

Virgin Independent Pilots Association (VIPA) president Captain John Lyons on Friday said his union of Virgin pilots supported an international review of cockpit safety procedures.

"VIPA and the wider pilot community have been concerned about a pilot's ability to access the cockpit under all circumstances," he said.

Australian pilots said that, in the Germanwings situation, a flight attendant in the cockpit might have been able to open the door and let the captain return to the flight deck.

"The most obvious reason you would have that system is for them to open the door," Australian and International Pilots Association president Nathan Safe said.

"Even having a flight attendant there isn't going to make the system foolproof. It is an additional person that can manually open the door. I can't see them having a wrestling match in the cockpit or fly the plane physically. That is getting far too creative in my view."

Other pilots agreed, saying it was unlikely a flight attendant would be able to make a distress call from the cockpit even if they were aware the descent - which in the Germanwings case wasn't so fast as to be alarming - was not in keeping with the flight plans.

However, one pilot said the mere presence of a flight attendant might make a pilot abandon plans to down the aircraft.

"Psychologically, the bloke looks across and doesn't feel like he's just killing himself," the pilot said of that scenario.

"On his own, with a locked door, it would be easier to feel removed."