| 1 | GCS | GCS Air Service, Inc. | Callsign: Galion, Name changed from Galion Crestline Service | USA | AVCODES |
| 2 | GCS | Galion Crestline Service | Callsign: Galion, Name changed to GCS Air Service | USA | AVCODES |
| 3 | GCS | Skyway Airline | Callsign: Sky Tec, | CR | AVCODES |
| 4 | GCS | GCS Air Service | | | ICAO1 |
| 5 | GCS | GEMINI CHARTER SERVICE | | | SCAC4 |
| 6 | GCSF | GULF, COLORADO & SANTA FE RAILWAY | | | PWRC |
| 7 | GCSF | Gulf, Colorado and Santa Fe Railway | | | RSRV |
| 8 | GCSI | GCS INTERMODAL LLC | | | SCAC4 |
| 9 | GCSK | GUTCO CONSTRUCTORA SA DE CV | | | SCAC4 |
| 10 | GCSR | Gulf, Colorado & San Saba Ry. | 1/1994-7/2000 | | NAKINA |
| 11 | GCSR | Gulf, Colorado & San Saba Ry. | 1/94-7/2000 | | NRHS |
| 12 | GCSR | GULF, COLORADO & SAN SABA RAILWAY | | | PWRC |
| 13 | GCSR | Gulf, Colorado and San Saba Railway | | | RSRV |
| 14 | GCSR | GULF COLORADO & SAN SABA RAILWAY | | | SCAC4 |
| 15 | GCST | GULFCOAST LOGISITCS | | | SCAC4 |
| 16 | GCSU | PEACOCK CONTAINER PTE. LTD. | | SGP | BIC |
| 17 | GCSU | G.C.S. CONTAINERS SERVICE SA | | | PWRC |
| 18 | GCSU | G.C.S. Containers Service | | | RSRV |
| 19 | GCSU | GRAND CHINA SHIPPING HONG KONG COMP | | | SCAC4 |
| 20 | GCSX | Gulf, Colorado & San Sabe Ry. | 7/2005 | | NAKINA |
| 21 | GCSX | Granite City Steel Co. | 7/1930-1/1941; 1/1943-4/1961 (not listed) | | NAKINA |
| 22 | GCSX | Granite City Steel Co. | 4/38-4/61 | | NRHS |
| 23 | GCSX | *GRANITE CITY STEEL CO. | | | PWRC |
| 24 | GCSX | *GULF, COLORADO & SAN SABA RWY. | | | PWRC |
| 25 | GCSX | RAIL LOGISTICS SERVICES INC | | | SCAC4 |
| 26 | GCSY | GARCIA, SAMUEL | | | SCAC4 |
| 27 | GCSZ | GULF CENTRAL SYSTEMS | | | PWRC |
