Announcing its temporary recommendation earlier this week, the EASA said that pilots must remain at their "assigned station" throughout the flight, "unless absence is necessary for the performance of duties in connection with the operation or for physiological needs".
At this point, the EASA added, one pilot can leave the cockpit provided "at least one suitably qualified pilot remains at the controls of the aircraft at all times".
The EASA also warned that "if we do publish a recommendation, it is not easily ignored."
But the Air France pilots' union quickly assailed what it described as a hasty recommendation by the EASA, saying the organization hadn't decided to wait for the end of the investigation into the Germanwings plane crash.
Several air carriers from Germany, Belgium, Norway, Australia and Canada have already signaled their readiness to stick to the EASA's recommendation.
Meanwhile, the crashed plane's flight recorders have reportedly indicated that the captain of the crashed jet yelled at 27-year-old co-pilot Andreas Lubitz to "open the damn door" as the captain desperately tried to get back into the locked cockpit.