After the service, I took a look at the fluids in the car. There is a tank marked coolant with F and L marks on it, and the the level of fluid in this tank was (significantly) below the L mark - it looks like there are about two cups total at the very bottom.
This means that you can book a round-trip ticket to Hawaii from anywhere Delta flies in the US, Canada, Mexico, Puerto Rico, or US Virgin Islands using Korean Air miles for only 25,000 miles in coach or 45,000 miles in Business Class.
Obviously 4.3 miles is in optimal conditions and is probably unsafe, but what about 2.5 miles? Would that be a distance I can regularly fly to without any worries of losing connection? As long as you can maintain a LOS you should be good out to 2.5-3 miles.