While the confusion over normal mode and alternate mode did play a role in the crash, the BEA report investigating the crash found the following six proximate causes [1]:<p><pre><code>    - temporary inconsistency between the measured speeds, likely as a result of 
      the obstruction of the pitot tubes by ice crystals, causing autopilot 
      disconnection and reconfiguration to alternate law;
    - the crew made inappropriate control inputs that destabilized the flight 
      path;
    - the crew failed to follow appropriate procedure for loss of displayed 
      airspeed information;
    - the crew were late in identifying and correcting the deviation from the 
      flight path;
    - the crew lacked understanding of the approach to stall;
    - the crew failed to recognize that the aircraft had stalled and 
      consequently did not make inputs that would have made it possible to 
      recover from the stall.
</code></pre>
Of those six, three can be attributed to skills atrophy: failure to follow procedure for loss of displayed airspeed information, lateness in identifying deviation from the flight path, and failure to recognize stall. These are all skills that pilots are taught when they&#x27;re certified to fly a given aircraft. The fact that they didn&#x27;t have them means that they forgot, or, in other words, they didn&#x27;t have enough ongoing training to keep their skills fresh for emergencies.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Air_France_Flight_447#Final_report" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Air_France_Flight_447#Final_re...</a>