The European Aviation Safety Agency recommended Friday that at least two people be present in the cockpit of planes at all times, following the apparently deliberate crashing of the Germanwings flight this week.
German and Austrian airlines earlier announced they would adopt the so-called "rule of two" which is already standard in the United States. The moves came after initial investigations into the Germanwings crash indicated co-pilot Andreas Lubitz may have deliberately crashed the Airbus A320 into a mountain in France on Tuesday, killing all 150 people aboard, after locking the captain out of the cockpit.
"[The European Aviation Safety Agency] publishes today a temporary recommendation for airlines to ensure that at least two crew, including at least one qualified pilot, are in the flight crew compartment at all times of the flight," the agency said on its website.
Strict procedures to securely lock cockpit doors have became standard since the September 11, 2001 attacks to prevent hijackers from taking control of civilian aircraft.
On Thursday, Canada ordered its airlines to also impose the two-person regulation, affecting Air Canada, Westjet and charter airline Air Transat.
The same day British airline easyJet, Norwegian Air Shuttle and Icelandair also confirmed policy changes.
On Friday, German aviation industry body BDL and the transport ministry agreed to the rule for Lufthansa, including its subsidiary Germanwings, as well as Air Berlin, Condor and TUIfly.
The move also affects two Austrian carriers - Austrian Airlines and Flyniki - subsidiaries of Lufthansa and Air Berlin respectively.
The measure will be put into place immediately, Austrian transport ministry spokeswoman Andrea Heigl said.
"We would like European regulation to be adopted as quickly as possible," she said. Hungary's low-cost Wizz Air also said it would adopt the two-crew rule. The EU said Friday it is studying whether to change the rules after the Germanwings disaster.