| B | SK | PERFORMING OPERATIONS; TRANSPORTING |
| B64 | KL | AIRCRAFT; AVIATION; COSMONAUTICS |
| B64B | UKL | LIGHTER-THAN-AIR AIRCRAFT (ground installations for aircraft in general B64F) |
| B64C | UKL | AEROPLANES; HELICOPTERS (air-cushion vehicles B60V) |
| B64D | UKL | EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLYING SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT |
| B64F | UKL | GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR |
| B64G | UKL | COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR (apparatus for, or methods of, winning materials from extraterrestrial sources E21C 51/00) |