On most planes, from Boeings to Cessnas but not Airbuses, the two sets of controls are linked, so that if you move the yoke (pitch/roll) or rudder pedals (yaw)

On most planes, from Boeings to Cessnas but not Airbuses, the two sets of controls are linked, so that if you move the yoke (pitch/roll) or rudder pedals (yaw) in one set they move in the other set. This means that one pilot knows what the other is doing. Airbuses average the two inputs by default, though either pilot can take control. SPOILER ALERT: A coffee spill was the cause of the plane crash in the movie Fate is the Hunter (1964), so I assume the risk is well-known.