Yep. That's for the condition. The pick up in combat environment or at sea or town... is very tricky ( you can see some topics about the pilot's behavior).
In the group leader init:
myfancygroup=group this;
Name your chopper:
myfancyhelo
Put this in the trigger init:
({_x in myfancyhelo} count units myfancygroup) == (count units myfancygroup)
that way, the trigger will only be activated when all the players in the group are in the chopper