• The difficulty of the final event is only indicative and can change a lot if there are zombies nearby.. so it is highly recommended to clean up the area first.
  
• The item needed to call the helicopter is the vanilla military walkie talkie, can generally be found in military chests.
  I've added a small chance that it will be found in the bodies of soldiers and police forces.
  
• Created and tested in singleplayer, for multiplayer in theory it should work, at least partially, but it is not guaranteed.
  
• The advanced antenna (Electrical category of the crafting menu) can be used to contact headquarters and can also be activated in repeater mode to increase radio signal strength.
  
• To reopen the extraction tracker gui right click in an empty space
  
• A new save is required
  
• English is not my native language, so please help me if any correction is needed, thank you