620 Engineering & allied operations
629 Other branches of engineering
629.1 Aerospace engineering
629.13 Aeronautics
629.132 Mechanics of flight; flying and
related topics
629.133 Aircraft types
629.134 Aircraft components and
general techniques
629.135 Aircraft instrumentation (Avionics)
629.136 Airports
629.3 Air-cushion vehicles (Ground
-effect machines,Hovercraft)
629.4 Astronautics