Here is what you do. You get on board and realise you and you child are seperated. Politely ask the cabin crew if they can help. If they can't or won't help, explain to them that you feel it is in the interest of safety for you and all people on board. If it still does not work let them know your displeasure and sit in your original seats. Keep a close eye and determine when the plane is about to close doors and get the cabin crews attention. Now you demand that you and your child be permitted to leave the airplane unless you sit with your kid. Tell them if they do not you will sue the entire crew including the captain for false imprisonment. A criminal offense by the way. You will definatly get there attention. At that point they can either sit you with your child or offload you, a process that will take at least thirty minutes.
Under normal circumstaces I would never be separated from my child while on an airplane.
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