| 7701 | CIPA | CLIPPER AIR FREIGHT FORWARDERS USA | | | SCAC3 |
| 7702 | CIPA | CRUCES INTERNACIONALES PEGAS | | | SCAC4 |
| 7703 | CIPB | CONTAINER INTERMODAL TRANSPORT INC | | | SCAC4 |
| 7704 | CIPC | CHIEPPO COACHES | | | SCAC3 |
| 7705 | CIPD | CITY PICKUP & DELIVERY | | | SCAC3 |
| 7706 | CIPE | CITGO PETROLEUM CORPORATION | | | SCAC3 |
| 7707 | CIPE | CRUSES INTERNACIONALES PE-GA | | | SCAC4 |
| 7708 | CIPG | CHELLARAM SHIPPING (HONG KONG) LTD | | | SCAC4 |
| 7709 | CIPI | CINCINNATI PIGGYBACK INT | | | SCAC3 |
| 7710 | CIPL | CITY OF PORTLAND | | | SCAC3 |
| 7711 | CIPM | CHIPMAN VAN & STORAGE INC | | | SCAC3 |
| 7712 | CIPN | CIPPONERI, TOM TRUCKING | | | SCAC3 |
| 7713 | CIPO | CITY PIONEER TRANSFER & STORAGE | | | SCAC3 |
| 7714 | CIPQ | CITY PARCEL DELIVERY | | | SCAC3 |
| 7715 | CIPS | AMEREN ENERGY GENERATING CO. [CENTRAL ILLINOIS PUBLIC SERVICE CORP.] | | | PWRC |
| 7716 | CIPS | CITRA ENTERPRISE | | | SCAC3 |
| 7717 | CIPT | CHIP TRUCKING INC | | | SCAC3 |
| 7718 | CIPU | CAI INTERNATIONAL | | USA | BIC |
| 7719 | CIPU | CAI International | | | RSRV |
| 7720 | CIPU | CONVOY INTERCONTINENTAL TRANSPORT | | | SCAC3 |
| 7721 | CIPU | CONTAINER APPLICATIONS INTERNATIONA | | | SCAC4 |
| 7722 | CIPV | CREATIVE IRON PATIO | | | SCAC4 |
| 7723 | CIPW | CHIPMAN RELOCATIONS | | | SCAC4 |
| 7724 | CIPX | Ameren Energy Generating Co. | 7/2000-7/2005 (not listed) | | NAKINA |
| 7725 | CIPX | Central Illinois Public Service Co. | added 10/1974; 1/1975-1/1980; eliminated 4/1993; 1/1994 (not listed); added 10/1995; eliminated 1/1999 | | NAKINA |
| 7726 | CIPX | College Inn Food Products Co. (Union Refrigerator Transit Co.) | 7/1935 | | NAKINA |
| 7727 | CIPX | College Inn Food Products Co. | 7/1932 | | NAKINA |
| 7728 | CIPX | Central Illinois Public Service Co. | added 10/74; 1/75-1/80; eliminated 4/93; 1/94; added 10/95; eliminated 1/99 | | NRHS |
| 7729 | CIPX | Ameren Energy Generating Co. | Jul-00 | | NRHS |
| 7730 | CIPX | *COLLEGE INN FOOD PRODUCTS CO. | | | PWRC |
| 7731 | CIPX | +AMEREN ENERGY GENERATING CO. [CENTRAL ILLINOIS PUBLIC SERVICE CORP.]} | | | PWRC |
| 7732 | CIPX | Central Illinois Public Service (Ameren Energy Generating) | | | RSRV |
| 7733 | CIPX | CENTRAL ILLINOIS EXPRESS INC | | | SCAC3 |
| 7734 | CIPY | CENTRAL OIL AND SUPPLY CORPORATION | | | SCAC3 |
| 7735 | CIPZ | AMEREN ENERGY GENERATING CO. [CENTRAL ILLINOIS PUBLIC SERVICE CORP.] | | | PWRC |
| 7736 | CIQA | CORPORATE CONTAINERS INC | | | SCAC4 |
| 7737 | CIQC | CIMPE CONTAINER SERVICE MIAMI FL | | | SCAC3 |
| 7738 | CIQC | CTI INC | | | SCAC4 |
| 7739 | CIQE | CARGO INTERNATIONAL LOGISTICS INC | | | SCAC4 |
| 7740 | CIQO | COC TRANSPORTATION INC | | | SCAC4 |
| 7741 | CIQP | CCI TRANSPORT & CRANE INC | | | SCAC4 |
| 7742 | CIR | Arctic Circle Air Service, Inc. | IATA: 5F, Callsign: Air Arctic, | USA | AVCODES |
| 7743 | CIR | Arctic Circle Air Service | IATA: 5F | | ICAO1 |
| 7744 | CIR | City of Rochelle, Illinois | 7/2000-7/2005 | | NAKINA |
| 7745 | CIR | City of Rochelle, Illinois | Jul-00 | | NRHS |
| 7746 | CIR | *CENTRAL IOWA RAILROAD | | | PWRC |
| 7747 | CIR | +CITY OF ROCHELLE, ILLINOIS | | | PWRC |
| 7748 | CIR | City of Rochelle, Illinois | | | RSRV |
| 7749 | CIR | CITY OF ROCHELLE ILLINOIS | | | SCAC4 |
| 7750 | CIRB | CIRCLE B CARRIERS | | | SCAC4 |
| 7751 | CIRC | Central Iowa Transportation Cooperative d/b/a Central Iowa Ry. Co. | 1/1975; eliminated 7/1976; 1/1980 | | NAKINA |
| 7752 | CIRC | Central Iowa Ry. Co. | added 4/1974 | | NAKINA |
| 7753 | CIRC | Central Iowa Ry. Co. | added 4/74 | | NRHS |
| 7754 | CIRC | Central Iowa Transportation Cooperative d/b/a Central Iowa Ry. Co. | 1/75; eliminated 7/76; 1/80 | | NRHS |
| 7755 | CIRC | *CENTRAL IOWA RAILWAY CO. | | | PWRC |
| 7756 | CIRC | *CONSOLIDATED INSPECTION & REPAIR CORP. | | | PWRC |
| 7757 | CIRD | CHICAGO INTERMODAL TRANSPORTATION I | | | SCAC3 |
| 7758 | CIRD | CHICAGO INTERMODAL TRANSPORTATION I | | | SCAC4 |
| 7759 | CIRF | CIRCLE FOUR TRANSFER INC | | | SCAC3 |
| 7760 | CIRG | CAL INLAND REFRIGERATED SERVICES IN | | | SCAC3 |
| 7761 | CIRH | CSI INTERNATIONAL INC | | | SCAC4 |
| 7762 | CIRI | CIRI - COLLINS LOGISTICS LLC | | | SCAC4 |
| 7763 | CIRJ | CIRCLE P | | | SCAC4 |
| 7764 | CIRM | CIRCLE M CARTAGE INC | | | SCAC3 |
| 7765 | CIRN | CIRCLE A CONSTRUCTION INC | | | SCAC3 |
| 7766 | CIRO | CAMDEN IRON & METAL INC/BANTIUOGLIO | | | SCAC3 |
| 7767 | CIRO | CAMDEN IRON & METAL INC | | | SCAC4 |
| 7768 | CIRP | CIRCLE P TRUCKING INC | | | SCAC3 |
| 7769 | CIRP | CIRCLE S TRANSPORTATION OF ARKANSAS | | | SCAC4 |
| 7770 | CIRQ | CIRCLE AIRFREIGHT CORP | | | SCAC3 |
| 7771 | CIRQ | CIRCLE AIRFREIGHT CORP | | | SCAC4 |
| 7772 | CIRR | Chattahoochee Industrial R.R. | 1/1975-7/2005 | | NAKINA |
| 7773 | CIRR | Chattahoochee Industrial R.R. | 1/75-7/2000 | | NRHS |
| 7774 | CIRR | CHATTAHOOCHEE INDUSTRIAL RAILROAD | | | PWRC |
| 7775 | CIRR | Chattahoochee Industrial Railroad | | | RSRV |
| 7776 | CIRR | CHATTAHOOCHEE INDUSTRIAL RAILROAD | | | SCAC3 |
| 7777 | CIRR | Chattahoochee Industrial Railroad | | USA | TRAFFIC |
| 7778 | CIRS | CIRCLE S TRANSPORT INC | | | SCAC4 |
| 7779 | CIRT | CAIRO SALT COMPANY INC | | | SCAC3 |
| 7780 | CIRU | CAROTRANS INTERNATIONAL | | | SCAC3 |
| 7781 | CIRU | COMMISSIONARIA INTERTRASPORTI SRL | | | SCAC4 |
| 7782 | CIRV | CIRCLE VAN & STORAGE INC | | | SCAC4 |
| 7783 | CIRX | Consbec Inc. | added 4/1997; 7/2000; eliminated 10/2001; 7/2005 (not listed) | | NAKINA |
| 7784 | CIRX | Consbec Inc. | added 4/97; 7/2000 | | NRHS |
| 7785 | CIRX | *CITY ISLAND RAILROAD, INC. | | | PWRC |
| 7786 | CIRX | +CONSBEC INCORPORATED | | | PWRC |
| 7787 | CIRX | Consbec | | | RSRV |
| 7788 | CIRY | Central Illinois R.R. Co. | 7/2005 | | NAKINA |
| 7789 | CIRY | CENTRAL ILLINOIS RAILROAD CO. | | | PWRC |
| 7790 | CIRY | Central Illinois Railroad | | | RSRV |
| 7791 | CIRY | CENTRAL ILLINOIS RAILROAD COMPANY | | | SCAC4 |
| 7792 | CIS | CIS Express Ukraine, Ltd. | Callsign: Express Ukraine, Ceased operations. | UA | AVCODES |
| 7793 | CIS | Cisalpino SA | | CH | VKM |
| 7794 | CISA | CALIFORNIA INTERSTATE TRANSPORT, INC | | | SCAC3 |
| 7795 | CISA | CRUCES INTERNACIONALES SAGA | | | SCAC4 |
| 7796 | CISC | *CAYMAN ISLAND SHIPPING CO. | | | PWRC |
| 7797 | CISC | CITIES SERVICE COMPANY, COPPERHILL, TENNESSEE | | | PWRC |
| 7798 | CISC | CAINE STEEL COMPANY (DIVISION OF LF | | | SCAC3 |
| 7799 | CISC | CISCO | | | SCAC4 |
| 7800 | CISD | Colonel's Island R.R. Co. | added 10/1982; 1/1994; eliminated 1/1999; 7/2000 | | NAKINA |
