| 1 | IRM | Mahan Airlines | IATA: W5, Callsign: Mahan Air, IATA Prefix: 537, Name changed to Mahan Air. | IR | AVCODES |
| 2 | IRM | Mahan Air | IATA: W5, Callsign: Mahan Air, IATA Prefix: 537, Name changed from Mahan Airlines. | IR | AVCODES |
| 3 | IRM | Mahan Air | IATA: W5 | | ICAO1 |
| 4 | IRM | INDIANA RAILWAY MUSEUM | | | PWRC |
| 5 | IRMC | IRION MACHINE LTD | | | SCAC4 |
| 6 | IRMO | IRON MOUNTAIN CANADA CORPORATION | | | SCAC4 |
| 7 | IRMR | Iron Ridge Railroad (Imagenary model railroad) | | USA | TRAFFIC |
| 8 | IRMS | IVACO ROLLING MILLS 2004 LP | | | SCAC4 |
| 9 | IRMT | INTERMODAL REPAIR MODIFICATION & TR | | | SCAC4 |
| 10 | IRMX | III TRANSPORTATION | | | PWRC |
| 11 | IRMZ | IOWA INTERSTATE RAILROAD, LTD. | | | PWRC |
| 12 | IRMZ | III Transportation | | | RSRV |
