There's no need for a Faraday cage to be grounded.
A car forms an acceptable Faraday cage to protect occupants when struck by lightning even when isolated by its rubber tires, and a plane can be struck by lightning thousands of feet from the ground and still protect its occupants (though the lightning will still damage electronics if they're in the current path through the machine).
A car forms an acceptable Faraday cage to protect occupants when struck by lightning even when isolated by its rubber tires, and a plane can be struck by lightning thousands of feet from the ground and still protect its occupants (though the lightning will still damage electronics if they're in the current path through the machine).