( CNN ) Andreas Lubitz , the co-pilot who authorities say deliberately crashed Germanwings Flight 9525 in France , passed all his tests and medical exams and gave no voluntary indication that he was unstable or mentally ill , Lufthansa CEO Carsten Spohr told CNN Thursday . `` We have at Lufthansa a reporting system where crew can report without being punished their own problems or they can report about problems of others without any kind of punishment . That has n't been used either in this case , so all these safety nets we are so proud of here have not worked in this case , '' Spohr said . Lubitz had been with Germanwings since September 2013 and had completed 630 hours of flight time after training at the airline 's flight center in Bremen , Germany , the company has said . Germanwings is the budget carrier for Lufthansa . The CEO said he did n't know much more than what has been released by French authorities : The captain left the cockpit , tried to regain access by knocking on the door and `` the door was either kept locked or not opened in the way it was supposed to be , and that for sure is a clear indication that the remaining pilot -- the co-pilot -- did n't want the captain to return . '' Had the copilot suffered a medical emergency -- as some experts speculated in the initial hours after the accident -- there are safety procedures in place so that the pilot can re-access the cockpit , he said . That is , `` unless the person on the inside locks it and this apparently has happened here , '' the CEO said . After the September 11 , 2001 , attacks , cockpit doors were manufactured to withstand manual force and small weapons , so there was `` no way to get back to the cockpit for the captain , '' he said . Spohr was asked why Lubitz was allowed to be alone in the cockpit . American airlines require that any pilot leaving the flight deck be replaced by a flight attendant , so that two people remain in the cockpit at all times , but that 's not the case with all airlines internationally , CNN aviation analyst David Soucie said . An 8-minute descent to death . A Lufthansa spokesman previously said that the airline complies with all German and European aviation regulations , something Spohr reiterated in his CNN interview . `` Most airlines around the world follow the same procedures as Lufthansa that in flight phases with low workload , the pilot can leave the cockpit -- especially for physical need -- and then he returns to the cockpit as fast as he can . That 's a global thing , most accepted procedure , which we have used at Lufthansa for many , many years , '' Spohr said . Asked if the airline might reconsider this policy in light of Tuesday 's crash , Spohr said it was possible . `` I think we look at that as well , but we should not put the whole system at stake just because of this terrible single accident , '' he said . The airline will be consulting with its own experts , aviation authorities and experts with other airlines to determine what , if any , of its procedures need to be bolstered to prevent future such accidents from occurring , Spohr said , adding that he stood strongly by the manner in which Lufthansa operates airplanes and trains its employees . `` We understand emotions after this terrible accident , but for us as professionals we need to ensure the safety focus of Lufthansa is in no way touched -- and I promise you it 's not -- and we will do our very , very best to even improve it further . '' Who was co-pilot Andreas Lubitz ? CNN 's Frederik Pleitgen conducted the interview in Cologne , Germany , and Eliott C. McLaughlin wrote the story from Atlanta . CNN 's Tim Hume contributed to this report .
`` So all these safety nets ... have not worked in this case , '' CNN CEO tells Lufthansa . There 's clear indication co-pilot `` did n't want the captain to return , '' Carsten Spohr says .