| 1 | IR | Iran National Airlines Corp. (Iran Air) | ICAO: IRA, Callsign: Iranair, IATA Prefix: 096, Name changed to Iran Air - The Airline of Islamic Republic of Iran | IR | AVCODES |
| 2 | IR | Illinois RailNet, Inc. | 7/2000-7/2005 | | NAKINA |
| 3 | IR | Illinois RailNet, Inc. | Jul-00 | | NRHS |
| 4 | IR | ILLINOIS RAILNET INC. | | | PWRC |
| 5 | IR | Illinois RailNet | | | RSRV |
| 6 | IR | ILLINOIS RAILNET INC | | | SCAC4 |
| 7 | IR | | | IL | TRAFFIC |
| 8 | IR | Indian Railways | | IN | VKM |
| 9 | IRA | Iran National Airlines Corp. (Iran Air) | IATA: IR, Callsign: Iranair, IATA Prefix: 096, Name changed to Iran Air - The Airline of Islamic Republic of Iran | IR | AVCODES |
| 10 | IRA | Iran Air | IATA: IR | | ICAO1 |
| 11 | IRA | Iran Air | | IR | TRAFFIC |
| 12 | IRAIL | Independent Railways of Australia Pts. | | AUS | TRAFFIC |
| 13 | IRAS | Imperial Russian Air Service | Императорскій военно-воздушный флотъ | RUE | TRAFFIC |
| 14 | IRAT | IDAHOROADS INC | | | SCAC4 |
| 15 | IRB | Iran Air Tours Co. | IATA: B9, IATA Prefix: 491, Name changed to Iran Airtour Airline. Desigantor B9 reinstated by IATA | IR | AVCODES |
| 16 | IRB | Iran Airtour Airline | IATA: B9, IATA Prefix: 491, Name changed to Iran Air Tours Co. Desigantor B9 reinstated by IATA | IR | AVCODES |
| 17 | IRB | Iranair Tours | | | ICAO1 |
| 18 | IRBD | IRONBOUND TRANSPORT | | | SCAC4 |
| 19 | IRBL | INTEGRA FARMS LTD | | | SCAC4 |
| 20 | IRBY | IRBY WAYNE OIL COMPANY | | | SCAC4 |
| 21 | IRC | Iran Asseman Airlines | IATA: EP, IATA Prefix: 815, Name changed to Iran Aseman Airlines | IR | AVCODES |
| 22 | IRC | Iran Aseman Airline | IATA: EP, Callsign: Aseman, IATA Prefix: 815, Name changed from Iran Asseman Airlines | IR | AVCODES |
| 23 | IRC | Iran Aseman Airlines | IATA: EP | | ICAO1 |
| 24 | IRC | Intercolonial Ry. of Canada (Canadian National Rys.) | 8/1920-7/1932 | | NAKINA |
| 25 | IRC | Canadian Government Rys. (Canadian National Rys.) | 8/1920-7/1932 | | NAKINA |
| 26 | IRC | Canadian Government Rys. (Canadian National Rys.) | 23-Jul | | NRHS |
| 27 | IRC | CANADIAN NATIONAL RWY. [INTERCOLONIAL RWY. OF CANADA] | | | PWRC |
| 28 | IRC | InterRegional Calatori | | RO | TRAFFIC |
| 29 | IRCC | INDIAN RIVER CONSTRUCTION CO | | | PWRC |
| 30 | IRCH | INTERNATIONAL PAPER (LAFAYETTE CONT | | | SCAC4 |
| 31 | IRCL | INDUSTRIAL RESIN RECYCLING INC | | | SCAC4 |
| 32 | IRCN | IROC TRANSPORT INC | | | SCAC4 |
| 33 | IRCU | INTRUSCO LLC | | RUS | BIC |
| 34 | IRCU | KRONOS SA | | | SCAC4 |
| 35 | IRCX | Island Creek Corp. | eliminated 7/1997 | | NAKINA |
| 36 | IRCX | Nationwide Railroad Leasing, Inc. | added 4/1966; 10/1966-4/1970; eliminated 1/1971 | | NAKINA |
| 37 | IRCX | Morrison Plan, Inc. | added 1/1962; 7/1965; eliminated 4/1966 | | NAKINA |
| 38 | IRCX | International Railway Car Leasing Co. | added 1/1959; 4/1961; eliminated 1/1962 | | NAKINA |
| 39 | IRCX | International Railway Car Co. | added 10/1954; 10/1957; eliminated 1/1959 | | NAKINA |
| 40 | IRCX | International Railway Car & Equipment Co. | 1/1945-7/1954 (not listed) | | NAKINA |
| 41 | IRCX | Indian Refining Co., Inc. | 8/1920-7/1932 | | NAKINA |
| 42 | IRCX | International Railway Car & Equipment Co. | Jan-52 | | NRHS |
| 43 | IRCX | International Railway Car Co. | 10/57; eliminated 1/59 | | NRHS |
| 44 | IRCX | International Railway Car Leasing Co. | added 1/59; 4/61; eliminated 1/62 | | NRHS |
| 45 | IRCX | Morrison Plan, Inc. | added 1/62; 7/65; eliminated 4/66 | | NRHS |
| 46 | IRCX | Nationwide Railroad Leasing, Inc. | added 4/66; 10/66-4/70; eliminated 1/71 | | NRHS |
| 47 | IRCX | Island Creek Corp. | eliminated 7/97 | | NRHS |
| 48 | IRCX | *INDIAN REFINING CO., INC. | | | PWRC |
| 49 | IRCX | *NATIONWIDE RAILROAD LEASING, INC. [MORRISON PLAN, INC.; INTERNATIONAL RAILWAY CAR LEASING CO.] | | | PWRC |
| 50 | IRCX | *RETIRED 08-15-91 ATP (0359) | | | PWRC |
| 51 | IRCX | *ISLAND CREEK CORP. | | | PWRC |
| 52 | IRCZ | ITEL RAIL CORPORATION | | | PWRC |
| 53 | IRD | Arvand Airlines | Callsign: Arvand, | IR | AVCODES |
| 54 | IRD | Arvand Airlines | | | ICAO1 |
| 55 | IRDI | INTEGRITY RETAIL DISTRIBUTION INC | | | SCAC4 |
| 56 | IRE | Pariz Air | Callsign: Parizair, | IR | AVCODES |
| 57 | IRE | Pariz Air | | | ICAO1 |
| 58 | IREB | IRELAND, ROBERT TRUCKING | | | SCAC4 |
| 59 | IREL | IRELAND, S D CONCRETE | | | SCAC4 |
| 60 | IRES | IRI TRUCKING | | | SCAC4 |
| 61 | IREX | IRECO, Inc. | added 10/1986; eliminated 1/1994; 1/1994-7/2005 (not listed) | | NAKINA |
| 62 | IREX | Indianapolis Refrigerator Express (Indianapolis Abbatoir Co.) | 8/1920-7/1930 | | NAKINA |
| 63 | IREX | IRECO, Inc. | added 10/86; eliminated 1/94; 7/2000 | | NRHS |
| 64 | IREX | *INDIANAPOLIS ABBATOIR CO. (INDIANAPOLIS REFRIGERATOR EXPRESS) | | | PWRC |
| 65 | IREX | *DYNO NOBEL, INC. | | | PWRC |
| 66 | IREX | +IRECO INC. [ILLINOIS RAILWAY EQUIPMENT CO.] | | | PWRC |
| 67 | IREX | IRECO | | | RSRV |
| 68 | IREX | DYNO NOBEL, INC. | | | SCAC4 |
| 69 | IREX | Irex / Meteor | City: Sosnowiec | PL | TRAFFIC |
| 70 | IRF | Ta-Air Airline | Callsign: Ta-Air, | IR | AVCODES |
| 71 | IRF | TA-Air Airline | | | ICAO1 |
| 72 | IRG | Iranian Naft Airlines | IATA: NV, Callsign: Naft, Name changed to Karun Airlines in September 2017. | IR | AVCODES |
| 73 | IRG | Naft Air Lines | | | ICAO1 |
| 74 | IRH | Atlas Aviation Group | Callsign: Atlas Avia, | IR | AVCODES |
| 75 | IRH | Atlas Aviation Group | | | ICAO1 |
| 76 | IRHN | IRONHORSE TRANSPORTATION | | | SCAC4 |
| 77 | IRHT | IRON HORSE TRANSPORT INC | | | SCAC4 |
| 78 | IRHX | IRON HORSE RAILROAD | | | PWRC |
| 79 | IRI | Navidtec | Callsign: Navid, | IR | AVCODES |
| 80 | IRI | Navid | | | ICAO1 |
| 81 | IRIA | Islamic Republic of Iran Armed Forces | | IR | TRAFFIC |
| 82 | IRIPK | Instytut Rozwoju i Promocji Kolei | | PL | TRAFFIC |
| 83 | IRIR | INTERPSPORT RACING INC | | | SCAC4 |
| 84 | IRIS | Irisbus | City: Name of the Iveco buses in 1999 - 2013, due to merger with Renault Bus. | I | TRAFFIC |
| 85 | IRIU | IRS INTERNATIONAL | | AUS | BIC |
| 86 | IRIV | IRIS NAVIGATION LIMITED | | | SCAC4 |
| 87 | IRIZAR | Irizar | Irizar Group (or simply Irizar) is a Spanish-based manufacturer of luxury buses and coaches. | E | TRAFFIC |
| 88 | IRJ | Bonyad Airlines | Callsign: Bonyad Air, | IR | AVCODES |
| 89 | IRJ | Bonyad Airlines | | | ICAO1 |
| 90 | IRK | Kish Air | IATA: Y9, Callsign: Kishair, IATA Prefix: 780, ICAO Designator changed to KIS. | IR | AVCODES |
| 91 | IRK | Kish Air | IATA: Y9 | | ICAO1 |
| 92 | IRKL | ISLANDER TRUCKING LLC | | | SCAC4 |
| 93 | IRKU | LTD IRTEK | | RUS | BIC |
| 94 | IRL | Irish Air Corps | Callsign: Irish, | IRL | AVCODES |
| 95 | IRL | Irish Air Corps | | | ICAO1 |
| 96 | IRLL | INNOVATIVE RESOURCES LLC | | | SCAC4 |
| 97 | IRLO | IRIE LOGISTICS LLC | | | SCAC4 |
| 98 | IRLQ | IRL | | | SCAC4 |
| 99 | IRLS | INTERIOR LOGISTICS SERVICES LTD | | | SCAC4 |
| 100 | IRLX | Western Railway Supply, Inc. | 7/2005 (not listed) | | NAKINA |
