All the above replies are true but a bit simplistic for larger air transport or biz jets. While ultimately all grounds end up connected to airframe, for ground loop & interference reasons each bus & signal type will be wired to a seperate grounding point in each area. These are normally divided by electrical bus type (AC or DC, Essential, Battery, Service etc) and whether power, signal or chassis. For aluminum airframes each ground wire is kept as short as possible from unit connector to ground but on composite aircraft like the Starship they were all run back to common grounding plates adjacent to the circuit breaker panels - a lot of extra weight & voltage loss.
BTW the electrical potentials on aircraft are kept as low as possible above ambient by means of the static wicks that are designed to leak away charge and thus reduce the possibility of lightning strikes.