Putting your penis's urethra right up to a girl's urethra and peeing, or vice versa. The pee goes up to the receiver's bladder so that they are all fueled up.
Mid-air Refueling is the act of space docking with the added bonus of diarrhea.
This is not true space docking, because the act resembles a refueling aircraft passing fuel to the other. A vaccuum seal is essential to success and cleanliness.