It will be mandatory for two people to be in the cockpit at all times on all international and domestic flights, the Federal Government says.

Authorities reviewed Australia's aviation regulations after 150 people were killed when a Germanwings plane crashed in the French Alps last week.

Co-pilot Andreas Lubitz has been blamed for the crash, and was alone in the cockpit when the plane slammed into the mountainside.

Deputy Prime Minister Warren Truss said the new policy would apply to aircraft with 50 or more passengers.

"There is no law in Australia that requires there to be two people on the flight deck at all times," Mr Truss said.

"One or two of the smaller airlines in Australia have such a policy, but it is not included in the operations manuals of most of our major airlines.

"This will mean that one of the flight attendants would come and sit in the cockpit if one of the pilots needed to leave the flight deck for any reason."

Mr Truss said the Government had been in discussion with the airlines over the past couple of days and there had been an agreement airlines in Australia would move immediately to adjust their flight operation procedures.

"It's very, very difficult to intervene in all of these circumstances because they are different in every case," Mr Truss said.

"But we certainly need to be sure that we are taking every possible step to make sure there isn't an incident of this nature in Australia and global aviation is as safe as possible."

Qantas and Virgin will have two people in cockpit

Qantas and Virgin Airlines have confirmed they will comply with the change of procedure and TigerAir has implemented the policy which will come into effect on March 31.

The Australian Pilots Association said having two people in cockpits at all times may not be as simple as it sounds.

Nathan Safe from the Pilots Association said there were a number of logistical and security hurdles.

"This certainly isn't going to be 100 per cent fool-proof," he said.

"I understand the Government needs to act and to be seen to be acting as well.

"We do welcome the policy but its practical implementation is where the actual difference is going to be made."

Cabinet's national security committee discussed the measure over the weekend as part of a review of Australia's aviation laws.

The black box voice recorder retrieved from the wreckage of the Germanwings flight revealed Lubitz, 27, locked his colleague out of the cockpit after he had left to go to the toilet during the flight from Barcelona to Dusseldorf.

Lubitz then apparently set the plane on course to fly into a mountainside in the French Alps, as the other pilot tried to break the cockpit door down.

Industry should conduct safety review

Former Boeing safety engineer Todd Curtis said the disaster would force airlines to take steps to try to ensure a similar incident did not occur again.

"The industry should sit down and figure out what combination of technology and procedures may have to change," Mr Curtis told NewsRadio.

"There are some steps that can be taken to prevent some kinds of negative pilot actions, but it won't prevent all of them."

Mr Curtis said current privacy laws made it difficult for airlines to detect instability among pilots.

"Unless it manifests itself in some way — for example someone does something, preferably outside of the cockpit, which draws attention to themselves or they self-report that they have a problem — there really is no way to objectively and consistently figure out if someone has a potentially dangerous psychological or psychiatric problem," he said.

"I might also add that in many countries the medical privacy laws that exist make it very difficult for any employer to ask about the specific private medical history of any individual."

Mr Truss said Australian pilots were subject to annual medical reviews which included a psychiatric assessment.

"If at any time there are concerns about the mental health of any pilot or co-pilot there are procedures in place to ensure that there is a medical intervention and those people are not placed in command of aircraft," he said.

"There is a constant review of aviation safety practices occurring and airlines around the world learn from incidents and ... ensure that these kind of issues are not repeated.

"There are now quite a number of cases, perhaps more than a dozen over the last 30 or 40 years, which are thought to be aircraft crashes resulting from pilot suicide.

"It's very, very difficult to intervene in all of these circumstances because they are different in every case, but we certainly need to be sure that we're taking every possible step to make sure there isn't an incident of this nature in Australia and that global aviation is as safe as possible."

As investigators sought to build a picture of Lubitz and any possible motives, media reports emerged that he suffered from a problem with his eye, adding to earlier reports he was severely depressed.

German prosecutors said they believed Lubitz hid an illness from his airline employer but did not specify the ailment.

They added he had been written off sick on the day the plane crashed.

The search for the plane's second black box is still continuing.

Germany is to hold a national memorial ceremony on April 17 for the victims of the disaster, half of whom were German, with Spain accounting for at least 50 and the remainder composed of more than a dozen other nationalities, including two Australians.