You're right, that pilot depends on jet fuel, of which there is only a finite amount in the tanks. "Bingo" is the point where they have enough fuel left in the tanks to get back to base safely. What? Are you thinking that the pilot will simply stop off at a gas station in the sky and refuel? Sorry, but tanker aircraft aren't always available, which is why pilots plan for the "bingo" point. Same thing for electric batteries, they aren't going to run them until they are completely dead, they are going to plan their battery levels and turn back at a certain point, just like they do for fueled vehicles.