| 901 | CAS | Christman Air System | | | ICAO1 |
| 902 | CAS | CITIZEN EXPRESS LINES | | | SCAC4 |
| 903 | CASA | CASA TRUCKING | | | SCAC4 |
| 904 | CASB | CASKEY BROTHERS | | | SCAC3 |
| 905 | CASB | CR AMERICAS SHIPPING COMPANY LIMITE | | | SCAC4 |
| 906 | CASC | CASS COUNTY PUBLIC TRANSPORTATION | | | SCAC3 |
| 907 | CASD | CASS INC | | | SCAC4 |
| 908 | CASE | CALIFORNIA SIERRA EXPRESS INC | | | SCAC4 |
| 909 | CASE | | | USA | TRAFFIC |
| 910 | CASF | CASSENS TRANSPORT COMPANY | | | SCAC3 |
| 911 | CASG | CASSERINOS | | | SCAC3 |
| 912 | CASI | CASSIL FREIGHT INC | | | SCAC3 |
| 913 | CASI | CASSIL FREIGHT INC | | | SCAC4 |
| 914 | CASJ | CASSITTO BROS MOVING & STORAGE CORP | | | SCAC3 |
| 915 | CASK | CASSCO REFRIGERATED TRANSPORT | | | SCAC3 |
| 916 | CASK | C A S TRUCKING | | | SCAC4 |
| 917 | CASL | CASTLE LINES INC | | | SCAC3 |
| 918 | CASL | CASS TRUCKING INC | | | SCAC4 |
| 919 | CASN | CASWELL VAN LINES | | | SCAC3 |
| 920 | CASN | CASTANEDA MORAN, JUAN CARLOS | | | SCAC4 |
| 921 | CASO | CP Rail (CASO) | added 7/1985; eliminated 10/1987; 1/1994-7/2005 | | NAKINA |
| 922 | CASO | Consolidated Rail Corp. | added 4/1976; eliminated 4/1977; 1/1980 | | NAKINA |
| 923 | CASO | Penn Central Transportation Co., Robert W. Blanchette, Richard C. Bond and John H. McArthur, Trustees | eliminated 4/1976 | | NAKINA |
| 924 | CASO | Penn Central Transportation Co. (Canada Southern Ry.) | 1/1975 | | NAKINA |
| 925 | CASO | Canada Southern Ry. (New York Central System) | 10/1966 | | NAKINA |
| 926 | CASO | Canada Southern Ry. | 1/1943-7/1965 | | NAKINA |
| 927 | CASO | Canada Southern Ry. | 1/52-7/65 | | NRHS |
| 928 | CASO | Canada Southern Ry. (New York Central System) | Oct-66 | | NRHS |
| 929 | CASO | Penn Central Transportation Co. (Canada Southern Ry.) | Jan-75 | | NRHS |
| 930 | CASO | Penn Central Transportation Co., Robert W. Blanchette, Richard C. Bond and John H. McArthur, Trustees | eliminated 4/76 | | NRHS |
| 931 | CASO | Consolidated Rail Corp. | added 4/76; 1/80 | | NRHS |
| 932 | CASO | *CONSOLIDATED RAIL CORP. [PENN CENTRAL TRANSPORTATION CO.; NEW YORK CENTRAL SYSTEM, CANADIAN SOUTHERN RWY.] | | | PWRC |
| 933 | CASO | +CP RAIL [CANADA SOUTHERN RY] | | | PWRC |
| 934 | CASO | Canada Southern Railway (Canadian Pacific Railway) | | | RSRV |
| 935 | CASO | CP RAIL (CASO) | | | SCAC3 |
| 936 | CASO | CP RAIL (CASO) | | | SCAC4 |
| 937 | CASO | Canada Southern Ry. | | CDN | TRAFFIC |
| 938 | CASP | CASTO TRAVEL CORP | | | SCAC3 |
| 939 | CASP | CHAMPS AUTO SPORT TRANSPORT | | | SCAC4 |
| 940 | CASQ | CASE CARTAGE INC | | | SCAC3 |
| 941 | CASR | CASCADE RECREATIONAL RAILROAD | | | PWRC |
| 942 | CASR | CASCO SERVICES INC | | | SCAC3 |
| 943 | CASS | CASS SCENIC RAILROAD (STATE OF WEST VIRGINIA) | | | PWRC |
| 944 | CASS | CASSIDYS TRANSFER & STORAGE LIMITED | | | SCAC4 |
| 945 | CAST | CAST NORTH AMERICA INC. | | | SCAC3 |
| 946 | CAST | CAUSTIC SODA TRANSPORTATION COMPANY | | | SCAC4 |
| 947 | CASU | HAPAG LLOYD A.G | | D | BIC |
| 948 | CASU | CAST NORTH AMERICA | | | SCAC3 |
| 949 | CASU | CP SHIPS | | | SCAC4 |
| 950 | CASV | CASTLE TRUCKING CO | | | SCAC3 |
| 951 | CASW | CARRIER TRANSPORT SERVICE OF CALIFO | | | SCAC3 |
| 952 | CASW | C A S TRANSPORTATION INC | | | SCAC4 |
| 953 | CASZ | CALIFORNIA STEEL, INC. | | | PWRC |
| 954 | CAT | Copenhagen Airtaxi | Callsign: Aircat, | DK | AVCODES |
| 955 | CAT | Copenhagen Airtaxi | | | ICAO1 |
| 956 | CAT | Civil Air Transport | IATA: CT | | ICAO1 |
| 957 | CAT | CALIFORNIA TRAILS INC | | | SCAC4 |
| 958 | CAT | City Airport Train | City: Wien | A | TRAFFIC |
| 959 | CAT | City Air Terminal BetriebsgmbH | | AT | VKM |
| 960 | CATA | CARGO TRANSPORT INC | | | SCAC4 |
| 961 | CATC | CAPITOL TRUCKING CO | | | SCAC3 |
| 962 | CATC | CAPITOL TRUCKING CO | | | SCAC4 |
| 963 | CATD | CASTERLING TRUCKING INC | | | SCAC3 |
| 964 | CATE | C A T TRUCK LINES | | | SCAC3 |
| 965 | CATH | CARTER, L F INC | | | SCAC3 |
| 966 | CATH | CAT TRANSPORTATION LLC | | | SCAC4 |
| 967 | CATI | CALIFORNIA TRUCKING AND TRANSPORTAT | | | SCAC3 |
| 968 | CATI | CHINA AHEAD TRUCKING INC | | | SCAC4 |
| 969 | CATK | CARTER TRUCKING COMPANY | | | SCAC3 |
| 970 | CATK | COBBS AUTO TRANSPORT LLC | | | SCAC4 |
| 971 | CATL | C A T S TRAVEL | | | SCAC3 |
| 972 | CATL | C A T S TRAVEL | | | SCAC4 |
| 973 | CATLV | Citizens Area Transit | City: Las Vegas | USA | TRAFFIC |
| 974 | CATM | CARLTON TRUCKING CO INC | | | SCAC3 |
| 975 | CATM | CARLTON TRUCKING CO INC | | | SCAC4 |
| 976 | CATO | CATO MOVING & STORAGE CO OF DOUGLAS | | | SCAC3 |
| 977 | CATO | CATALINA OFFSHORE PRODUCTS | | | SCAC4 |
| 978 | CATP | CAR MATE TRAILERS INC | | | SCAC4 |
| 979 | CATP | Caterpillar | | | TRAFFIC |
| 980 | CATQ | CANNING TRUCK SERVICE | | | SCAC3 |
| 981 | CATR | CANDEE ANN TRUCK LINES | | | SCAC3 |
| 982 | CATS | CASA TALAMANTES | | | SCAC4 |
| 983 | CATT | CAPITOL MOVING & STORAGE CO INC | | | SCAC3 |
| 984 | CATU | CARU CONTAINERS BV | | NL | BIC |
| 985 | CATU | CATU CONTAINERS SA | | | PWRC |
| 986 | CATU | CATU Containers | | | RSRV |
| 987 | CATU | COMPAGNIE DE TRANSPORT | | | SCAC3 |
| 988 | CATU | CONTAINER ASSOCIATION ROTTERDAM BV | | | SCAC4 |
| 989 | CATV | CATER INC | | | SCAC3 |
| 990 | CATW | CATON VAN & STORAGE COMPANY | | | SCAC3 |
| 991 | CATX | General American Marks Co. | added 1/2004; 7/2005 | | NAKINA |
| 992 | CATX | Canadian Tank Car Co. (Canadian General Transit Co., Ltd.) | 7/1932 | | NAKINA |
| 993 | CATX | *CANADIAN TANK CAR CO. (CANADIAN GENERAL TRANSIT CO., LTD.) | | | PWRC |
| 994 | CATX | +GENERAL AMERICAN MARKS CO. | | | PWRC |
| 995 | CATX | GENERAL AMERICAN MARKS COMPANY | | | SCAC4 |
| 996 | CATY | CROWLEY AMERICAN TRANSPORT | | | SCAC3 |
| 997 | CATZ | CATERPILLAR INC. | | | PWRC |
| 998 | CAU | Cancun Avioturismo, S.A. | Callsign: Avioturismo, | MEX | AVCODES |
| 999 | CAU | Canarias Aeronautica, S.L. | Callsign: Canarias Link, | E | AVCODES |
| 1000 | CAUA | CAUCASUS EXPRESS | | | SCAC4 |
