Airlines in New Zealand and Canada are among many others to have adopted the so-called ‘rule of two’ in recent days since it emerged that co-pilot Andreas Lubitz locked his captain out of the cockpit of flight 4U 9525 from Barcelona to Dusseldorf before crashing the Germanwings Airbus A320 into a mountain with the loss of 150 lives.

The victims included Australian woman Carol Friday, 68, and her son, Greig, 29, who both came from Melbourne.

The safety measures announced by Australian transport minister Warren Truss will apply immediately to all domestic and passenger planes carrying 50 or more people. Airlines affected include Australian flag-carrier Qantas, as well as Virgin Australia and Jetstar.

The new guidelines were announced just hours before prosecutors in Dusseldorf confirmed today that 27-year-old Lubitz received treatment for suicidal tendencies some years ago.

“The airlines will be acting immediately to implement this change and we’d expect to see this policy in place within hours on our major airlines,” said Mr Truss.

Qantas said in a statement that it would have two approved people in the cockpit at all times. The airline said that if one pilot needed to leave the cockpit another authorised person would occupy the jump seat – as distinct from the control seats occupied by the captain and co-pilot – until they returned.

Nathan Safe, president of the Australian and International Pilots Association, told AAP he was not convinced the new policy would have prevented the Germanwings crash, but added: “We understand that it is important the government acts and treats safety as its most important consideration.”

It is believed that Lubitz put last Tuesday’s ill-fated flight into an accelerated descent after locking pilot Patrick Sondheimer out the cockpit when he went to the toilet. Mr Safe’s reservations about the rule-of-two may revolve around whether other members of the cabin crew would necessarily have been capable of overpowering or reasoning with Lubitz even had they been in the cockpit.