Police are searching Lubitz's house and his background for clues on why he would commit such an act with unconfirmed reports that he may have suffered from depression.
On Friday, a press statement on the website of the German prosecutors office in Dusseldorf said that a search of Lubitz's house found no suicide letter but found documents with medical content which seemed to suggested Lubitz had hidden an illness from his employer. They did not say what illness.
Read MoreGermanwings co-pilot hid illness: Prosecutors
In a statement published on its website on Friday afternoon, Germanwings said: "Currently there is media coverage that the co-pilot of flight 4U 9525 was given a sick note for the day of the accident on Tuesday. Germanwings declares that a sick note for this day was not submitted to the company."
"This corresponds to the insights of the senior prosecutor of Dusseldorf. According to these insights, 'a torn-up current sick note, also—valid for the day of the incident' was found in the co-pilot's documents.
"According to the prosecutor's statement, this 'would—according to preliminary evaluation - support the assumption that the deceased had concealed his illness towards his employer and his occupational environment.'"
Following the revelations, there have been calls for more mental health checks on pilots.
The Civil Aviation Authority in the U.K. said in a statement Thursday that it was working with its European counterparts and had contacted UK operators to review procedures on pilots' health. It said, however, that adequate checks were already in place.
"All U.K. airline pilots undergo extensive and regular medical assessments to determine their fitness to hold a licence. As part of this, aeromedical examiners are required to assess a commercial pilot's mental health at each medical examination which, for an airline pilot flying with at least one other pilot, is undertaken annually. These detailed medical assessments are in line with international aviation standards."
Some are skeptical that the changes can work, however, not least of all the chief executive of Lufthansa, Carsten Spohr. Speaking at a press conference in Cologne Thursday that "you can never exclude such an individual event", adding, "no system in the world could manage to do that."
Anil Padhra, a senior lecturer in aviation studies at the University of Kingston near London, told CNBC Friday that new technology could be the way to ensure that the Germanwings disaster is not repeated in future.
Planes could be fitted with computer software that overrides potentially dangerous actions by pilots, or aviation authorities on the ground could take control of planes if necessary—even retrofitting toilets in the cockpit, Padhra said, although he thought that option unlikely.
"We have driverless trains and driverless cars so we could, in theory, have driverless planes in future. But I think that actually there would be a big kick back against that from the public, aviation unions and airplane manufacturers too, as those companies also tend to have pilot training schemes in place and derive a lot of revenues from them."
Although technology might be a solution to prevent another Germanwings disaster, the public still trust human beings more than computers to fly their plane, he said. "In theory, there are technological solutions but I think it will be a few years before we even see glimpses of these."