Every part of an aircraft's structure is electrically bonded to every other part such that there is no significant potential diff. across it.This is tested during manufacture (most of the time) down to fractions of an Ohm.It is necessary to bond an a/c structure as carbon impregnated tyres can only dissipate high voltages(watch an a/c arcing a few feet before touchdown at night).
Cars are not electrically bonded throughout their structure (hence no bonding leads and slight difference in price).No point therefore putting a bonding lead between car and pump.
As I think someone said if you put your hand on the metal part of your door frame before your foot touches the ground you will no longer be zapped.
ELECTICITY IS THE ART OF LUCIFER.