Australia has responded to the Germanwings air disaster by ordering that at least two crew members be present at all times in cockpits of larger domestic and international airliners.
Deputy prime minister Warren Truss said airlines including Qantas and Virgin Australia would implement the changed security protocols from today.
It will apply to all commercial flights with a least two flight attendants or more than 50 passengers. A flight attendant would enter the flight deck if one of the two pilots left it for any reason.
Previously, most Australian airlines have allowed their pilots to be alone on the flight deck.
French prosecutors blame co-pilot Andreas Lubitz, 27, for the crash of Flight 9525 that claimed 150 lives in southern France last week. The cockpit voice recorder has revealed that the pilot had been shut out of the cockpit when the Airbus A320 crashed.
Mr Truss said there were already mental illnesses that stopped sufferers from being pilots in Australia and that pilot health was assessed regularly.
"There is a need to balance the fact that people with proper treatment can recover from mental illness and be able to undertake normal careers with the critical priority of ensuring that aircraft are always safe," he told reporters.
"So this is a challenging issue for airlines and indeed for that matter for other employers, to be fair to their employees who have mental health issues but at the time ensuring that those mental health issues do not put at risk the lives of other Australians."
Pilot suicide is one of the theories behind the disappearance of Malaysia Airlines Flight 370, which flew far off course during a flight from Kuala Lumpur to Beijing on March 8 last year and is believed to have crashed off the Australian coast with 239 passengers and crew on board.
Mr Truss said pilot suicide was suspected behind more than a dozen plane crashes over the past 40 years.