I am still surprised to see how many refueling operators are removing the bonding/grounding leads at the end of the refueling, before the refuel hose is disconnected. Although I do understand that any difference in potential should have leveled out, there is still a small risk. Lack of training or disregarding the rules to save a few seconds?
This is a good point to bring up. And static charge associated with petrochemical handling is a complex issue.
For those who think a single momentary discharge is sufficient to equalize static charges, read up on dielectric absorption (
Dielectric absorption - Wikipedia, the free encyclopedia). And keep in mind that petrochemicals (i.e. fuel) make excellent dielectrics for charge storage. After disconnecting the ground lead, it is possible that a voltage differential can build up again between conductive parts (airplane and bowser tanks).