The Unknown Compulsory is the last flight of the contest, and serves as a final elimination flight. Published by CIVA at the contest, it is different at every contest throughout the year. Serious competition pilots will fly practice the figures that can be expected in an Unknown, and combinations of them, but no pilot has a chance to practice the Unknown at a contest before flying it. That is the essence of the flight, and the true challenge of the contest overall.
The 1996 WAC Unknown, shown below as flown left to right into a wind coming from the right, consists of 16 compound Aresti figures. Each pilot carries a copy of the Unknown mounted on the cockpit instrument panel for rapid reference during a flight. See "Ballet in the Sky" for a description of flying the Unknown.