(under the class definition) Devices for slowing the progress of aircraft or for holding or restraining them from movement.
(1) Note. this subclass includes also devices separate from the aircraft for retarding or restraining the aircraft. The search for external retarding or arresting mechanism should be continued in this class, subclass 63, for devices intended primarily to launch but usable also to retard.
(2) Note. For devices retarding the progress of water supporting member through the water, see Class 114, Ships, subclass 145.
