Mexico became the latest country on Monday to require the presence of two airline crew members in cockpits at all times, following the apparently deliberate Germanwings crash by the co-pilot.
The transport ministry said it will issue new rules requiring that an authorized and specially-trained crew member stay in the cockpit when one of the pilots needs to get out.
"This is a measure to strengthen operational security to guarantee that a person can help the pilot in the cockpit open the door at any time in planes with armored or reinforced cockpits," civil aviation director general Gilberto Lopez told a news conference.
When a pilot needs to leave the cockpit, the captain will call in a crew member familiar with how to open or close the door, but that person will not be allowed to sit in the pilot's seat, Lopez said.
Before the pilot leaves, the autopilot will have to be turned and the cockpit's oxygen masks must be ready for use. A curtain will have to be drawn so that passengers stay away from the cockpit door.
The "rule of two," which has been standard in the United States, was adopted by airlines and aviation authorities in several countries after the Germanwings crash in the French Alps last week.
French officials say the Germanwings plane's black box voice recorder indicates that Andreas Lubitz, 27, locked the captain out of the cockpit and steered Flight 4U 9525 into a mountainside.
They say that the more senior pilot tried desperately to reopen the door during the Barcelona to Duesseldorf flight's eight-minute descent after he left to use the toilet.
Germany's Bild newspaper, citing cockpit recorder data, said the senior pilot shouted "open the damn door" to a silent Lubitz as the screams of passengers are heard before the crash.
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