Andreas Lubitz worked for the company before he deliberately crashed a plane carrying 149 other people into the French Alps on March 24, 2015.
The final report on the crash by French investigators found he had suffered from a psychiatric condition and had been taking medication before the crash.
In 2013 he joined Lufthansa's low budget airline, Germanwings.
Lufthansa are considering dropping the 'four-eyes' principle (stock image)
He initially worked as a flight attendant before starting his role as co-pilot.
Lubitz prevented his colleagues and flight captain from entering the cockpit before deliberately plunging the plane into a mountain.
At the time, airlines, security authorities and politicians agreed to a “four-eyes” principle at all times in the cockpit, saying this could have prevented the disaster.
Chilling images depict the Germanwings crash Fri, March 24, 2017
The crash was deliberately caused by the co-pilot, Andreas Lubitz, who had previously been treated for suicidal tendencies and declared 'unfit to work' by a doctor
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Rescue workers and gendarmerie continue their search operation near the site of the Germanwings plane crash near the French Alps on March 26, 2015 in La Seyne les Alpes, France
The recommendation was that a flight attendant enter the cockpit as soon as one of the two pilots leaves.
This way the flight attendant could open the cockpit door from the inside and let the second pilot in.
But according to a report by the news magazine Focus, Lufthansa is now questioning the principle.
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The magazine said that according to the airline, the decision "has not yet been taken".
Carsten Spohr, chief executive officer of Deutsche Lufthansa AG (R) and Ulrik Svensson
Lufthansa's pilots (including Swiss, Austrian Airlines, Eurowings) reported however that flight attendants are to be exempted from cockpits as of May.
Air Berlin, Condor and TUIfly are also currently checking the rule, while Germania and Ryanair want to stick to the principle, according to the report.
The cockpit union association Cockpit views the regulation with scepticism now, reports Focus, due to the change of personnel the door to the cockpit remained open for too long, which could help terrorists take over the plane.
Only in rare cases, such as the Germanwings crash, the presence of two people would really provide more security.
The Germanwings co-pilot Andreas Lubitz
The flight attendant organisation UFO now sees the regulation as "pure show" introduced two years ago "to calm the public".
There had been no serious attempts on airlines to train the cabin crew for new tasks in the cockpit – not to mention emergency manoeuvres or fighting for the door lock with the out-of-control pilots.
UFO also doubts that flight attendants in the cockpit might be able to prevent pilots from crashing machines at all.
In the USA on the other hand the powerful aviation authority, FAA, has long been imposing the principle of the two-man rule.
The objections of the Europeans were considered to "not be comprehensible", according to Focus.