Brangdon while it is true that a faraday cage does not have to be grounded. It functions better if you drain the build up of charge to ground.

A hardened aircraft will build up a charge from an EMP burst. But they can also build up charges just from flying. These either slowly discharge to the air or when the plane lands.

The charge built up on something as small as an Altoids tin would disipate through the body. But would be so slight it probably would not even be noticed or at most a slight tingle.