| 1 | CLU | Avanti Aviation Aachen Luftfahfitgesellschaft mbH | Callsign: Carolus, Name changed to Triple Alpha Luftfahfitgesellschaft mbH. Founded in 1995 | D | AVCODES |
| 2 | CLU | Club Air (Europe) Ltd. | Callsign: Club, | GB | AVCODES |
| 3 | CLU | Triple Alpha Luftfahfitgesellschaft mbH | Callsign: Carolus, Ceased operation in July 2011. Name changed from Avanti Aviation Aachen Luftfahfitgesellschaft mbH. Entered administration in July 2011 | D | AVCODES |
| 4 | CLU | Cargologicair Ltd. | IATA: P3, Callsign: Firebird, IATA Prefix: 560, Ceased operations on 24 February 2020. AOC Reinstated on 22/04/2020. Part of Volga-Dnepr Group. | GB | AVCODES |
| 5 | CLU | Triple Alpha | | | ICAO1 |
| 6 | CLU | CROWN LIMOUSINE SERVICE | | | SCAC4 |
| 7 | CLUA | CONCEPTUM LOGISTICS (USA) LLC | | | SCAC4 |
| 8 | CLUB | COLUMBIA TUG BOAT CO | | | SCAC3 |
| 9 | CLUB | CLUB CAR INC | | | SCAC4 |
| 10 | CLUB | Club Transportation | | USA | TRAFFIC |
| 11 | CLUC | CONNECTICUT LUMBER CARRIERS INC | | | SCAC3 |
| 12 | CLUC | CASTILLO CORONADO, LUCINA | | | SCAC4 |
| 13 | CLUE | COLUMBIA EXPORT PACKERS INC | | | SCAC3 |
| 14 | CLUG | COLUMBUS AIR CARGO | | | SCAC3 |
| 15 | CLUH | CLOUGH, H R | | | SCAC4 |
| 16 | CLUI | C L U INC | | | SCAC3 |
| 17 | CLUJ | CARROLL TRUCK LINES (A DIVISION OF | | | SCAC3 |
| 18 | CLUJ | Compania de Transport Public | City: Cluj | RO | TRAFFIC |
| 19 | CLUK | COLLINS, LUKE | | | SCAC3 |
| 20 | CLUL | CLASSIC TRUCK LINES | | | SCAC3 |
| 21 | CLUM | COLUMBIA TRANSFER INC | | | SCAC3 |
| 22 | CLUN | CLUNE TRANSFER | | | SCAC3 |
| 23 | CLUN | CLUNE TRANSFER | | | SCAC4 |
| 24 | CLUP | COLUSSY TRUCKING INC | | | SCAC3 |
| 25 | CLUP | CLARK TRUCK PARTS INC | | | SCAC4 |
| 26 | CLUQ | CASTENS, LOUIS | | | SCAC3 |
| 27 | CLUR | CLOUTIER-LOTT ENTERPRISES, INC | | | SCAC3 |
| 28 | CLUR | CAL STATE AUTO PARTS INC | | | SCAC4 |
| 29 | CLUS | CLAUSSEN, THOMAS E | | | SCAC3 |
| 30 | CLUT | CLEVELAND UNION TERMINALS COMPANY | | | PWRC |
| 31 | CLUT | CLOUTIER, NORMAND TRANSPORT INC | | | SCAC3 |
| 32 | CLUV | COLUMBUS MOVING & STORAGE INC | | | SCAC3 |
| 33 | CLUX | Chillicothe Lumber Co. | added 10/1974; 1/1975; eliminated 10/1977 | | NAKINA |
| 34 | CLUX | Chillicothe Lumber Co. | added 10/74; 1/75 | | NRHS |
| 35 | CLUX | CHILLICOTHE LUMBER CO. | | | PWRC |
| 36 | CLUY | COMMERCIAL TRANSPORTATION INC | | | SCAC3 |
