| 1 | IRT | Irtysh Avia | IATA: IT, Callsign: Irtysh, Designator IT reinstated by IATA | KZ | AVCODES |
| 2 | IRT | Interot Airways | IATA: IQ, Callsign: Interot, IATA Prefix: 614, Name changed to Augsbury-Airways GmbH. Founded in 1980. | D | AVCODES |
| 3 | IRT | Irtysh-Avia | IATA: IT, Callsign: Irtysh, Designator IT recalled by IATA | KZ | AVCODES |
| 4 | IRT | Irtysh-Avia | Callsign: Irtysh, Designator IT recalled by IATA | KZ | AVCODES |
| 5 | IRT | Toos Airlines | Callsign: Toos Air, | IR | AVCODES |
| 6 | IRT | Irtysh Airlines | IATA: IT | | ICAO1 |
| 7 | IRT | Interborough Rapid Transit | City: New York | USA | TRAFFIC |
| 8 | IRTD | INDIAN RIVER TRANSPORT LTD | | | SCAC4 |
| 9 | IRTF | IRVIN TRANSFER | | | SCAC1 |
| 10 | IRTF | I & T TRANSFER | | | SCAC4 |
| 11 | IRTM | INTEGRATED RECYCLING TECHNOLOGIES I | | | SCAC4 |
| 12 | IRTN | INTER RAIL TRANSPORT LIMITED | | | SCAC4 |
| 13 | IRTR | INTERMOUNTAIN RIGGING & | | | SCAC4 |
| 14 | IRTS | INGERSOLL-RAND TRANSPORTATION SERVICES COMPANY | | | SCAC1 |
| 15 | IRTS | INGERSOLL-RAND TRANSPORTATION SERVI | | | SCAC4 |
| 16 | IRTT | European Rail Transport Feroviar | | RO | TRAFFIC |
| 17 | IRTU | ISOTANK SERVICES LIMITED | | | SCAC4 |
| 18 | IRTX | INTER-RAIL TRANSPORT | | | PWRC |
| 19 | IRTX | Inter-Rail Transport | | | RSRV |
| 20 | IRTX | INTER-RAIL LINK | | | SCAC4 |
