EU aviation safety authorities issued a recommendation for European airlines Friday (27 March) saying that at least two people should be in airplane cockpits at all times.

The recommendation - by the European aviation safety agency (EASA) - follows the crash of a Germanwings airplane on Tuesday (24 March) that killed 150 people in the French Alps.

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The co-pilot, Andreas Lubitz, is said to have deliberately flown the Barcelona-Duessdeldorf flight into a mountain.

Crash investigators say he locked himself in the cockpit when the captain left to use the bathroom.

"The agency makes this recommendation based on the information currently available following the dramatic accident […] and pending the outcome of the technical investigation,” the EASA said in a statement.

"This recommendation may be reviewed in the light of any new information concerning the accident," the agency added.

EASA recommendations are not binding but "they have weight", said an EU aviation safety official.

Until now EU rules stated that a flight crew should stay in the cockpit, except for physiological or operational needs.

While US airlines have had rules for a long time that say there should be two people in the cockpit at all times, the EU had issued no such requirement so far.

"This is because on EU airplanes, it is possible to see from both pilot seats who is on the other side of the door. In other parts of the world, there is no CCTV for the cockpit door. That is why there is another person in the cockpit," said a EU aviation safety source on Friday before the recommendation was issued.

Some European airlines had already decided themselves to add a second crew member in the cockpit.

After Norwegian Airlines on Thursday, EasyJet, Virgin Atlantic and Monarch revised their policy.

On Friday morning EU sources said that they were "consulting with the airline industry and member state about what would be appropriate or feasible, what would be the impact and side effects.”

EU aviation authorities also did not exclude a change in the rules - adopted after the 11 September 2001 attacks in the US - which require armoured-plated locked doors in the cockpit.

"The case of a pilot locking himself in was not considered when this rule was introduced. It was only made against unlawful entrance in the cockpit," said an official, pointing out that hijacking has almost disappeared thanks to these measures.

"Now we’re asking ourselves obvious questions. Action can be taken at EU level, but it would also have to be addressed at international level," the source added.

Meanwhile, the psychological profile of Andreas Lubitz has prompted questions about how to ensure that pilot are better screened for possible problems.