Airlines around the world on Thursday began requiring two crew members to always be present in the cockpit, after details emerged that the co-pilot of Germanwings Flight 9525 had apparently locked himself in the cockpit and deliberated crashed the plane into the mountains below.

Leading European budget airlines Norwegian Air Shuttle and EasyJet, along with Air Canada, say they will now require a minimum of two crew members in the cockpit while a plane is in the air.

Following the Sept. 11, 2001 terrorist attacks, U.S. airlines revamped their policies regarding staffing in the cockpit.

Whenever the door is open, flight attendants create a barrier between the cockpit and passengers. Typically, that is done with a beverage cart but some jets are outfitted with a mesh wire barricade. If a pilot leaves to use the bathroom, one of the flight attendants takes his or her seat in the cockpit.

Some European airlines, like Finnair, operated under similar procedures. But many did not prior to Tuesday's Germanwings crash, which killed all 150 people aboard the plane as it slammed into a mountainside in the French Alps.

Norwegian spokeswoman Charlotte Holmbergh-Jacobsson says the new rules will be adopted "as soon as possible" on all commercial flights globally. She said that the airline's security department had been thinking about the measure "for a while, and today decided on it."

 

Air Canada says it will implement its change "without delay." EasyJet says its new rules will take effect Friday.