Linear Momentum stays constant unless external force is applied. Angular Momentum stay constant unles external torque is applied. I and w can change Divers, Gymnasts and other athletes in flight maintain constant angular momentum throughout the flight.
Cats can turn over in mid air after being dropped back first, feet up.
Twisting dives and vaults can initiate the twisting phase of the maneuver in mid-flight. This DOES NOT violate conservation of angular momentum. Angular momentum changes distribution during the dive, but the total angular remains constant.