The Germanwings plane crash in the French Alps Tuesday has already promoted changes to airline cockpit security.

Following reports that co-pilot Andreas Lubitz locked out his fellow pilot from the cockpit on Flight 9525, several airlines announced they will begin to enforce the U.S. rules requiring two people at the cockpit at all times.

Lufthansa, the parent of Germanwings, issued a statement Friday saying it was moving to the "rule of two" policy over the entire airline group, which includes Swiss International Air Lines, Brussels Airlines, Austrian Airlines, Eurowings, and smaller regional airlines, as a "precautionary measure."

This follows a string of other airlines, including Air Canada, Westjet, Norwegian Air Shuttle, Air Berlin, Thomas Cook and budget carrier Easyjet.  

“The safety and security of its passengers and crew is the airline’s highest priority,” Easyjet said in a statement.

Virgin Atlantic and Monarch say that while a two crew policy has always been common practice, they are in the process of making this formal policy.

British Airways has so far refused to comment on the policy of its cockpit manning levels and says it does not discuss security issues, Sky News reports.

Emirates Airline said it has “today implemented a new operating policy where there would always be two crew members in the cockpit.” The new guidance “is effective immediately,” a spokesman said.

The new procedures will mean that two crew members must always be present on the flight deck.  U.S. airlines have long required another crew member, such as a flight attendant, to enter the cockpit when one of two pilot exits. The crew member must lock the door and remain inside until the pilot returns, according to the Federal Aviation Authority.

Investigators believe Lubitz intentionally crashed the plane into a mountainside during Tuesday’s flight from Barcelona to Duesseldorf, killing all 150 onboard.