| 1 | GIO | Regionnair, Inc. | IATA: RH, Callsign: Gionnair, Ceased operations on 01 June 2001. | CDN | AVCODES |
| 2 | GIO | Guinee Paramount Airlines S.A. | Callsign: Guipair, Name changed to Oceanic Airlines Inc. | GUI | AVCODES |
| 3 | GIO | Oceanic Airlines Inc. | IATA: O2, Designator O2 recalled by IATA. Name changed from Guinee Paramount Airlines S.A. | GUI | AVCODES |
| 4 | GIO | Gio d.o.o. | Callsign: Gio-Avia, | SLO | AVCODES |
| 5 | GIOS | GILS OIL SERVICE INC | | | SCAC4 |
| 6 | GIOX | Gilliland Oil Co. (Reserve Petroleum Co.) | 7/1930 | | NAKINA |
| 7 | GIOX | Gilliland Oil Co. | 8/1920-7/1923 | | NAKINA |
| 8 | GIOX | RESERVE PETROLEUM CO. [GILLILAND OIL CO.] | | | PWRC |
