| 2801 | IREX | IRECO | | | RSRV |
| 2802 | IREX | DYNO NOBEL, INC. | | | SCAC4 |
| 2803 | IREX | Irex / Meteor | City: Sosnowiec | PL | TRAFFIC |
| 2804 | IRF | Ta-Air Airline | Callsign: Ta-Air, | IR | AVCODES |
| 2805 | IRF | TA-Air Airline | | | ICAO1 |
| 2806 | IRG | Iranian Naft Airlines | IATA: NV, Callsign: Naft, Name changed to Karun Airlines in September 2017. | IR | AVCODES |
| 2807 | IRG | Naft Air Lines | | | ICAO1 |
| 2808 | IRH | Atlas Aviation Group | Callsign: Atlas Avia, | IR | AVCODES |
| 2809 | IRH | Atlas Aviation Group | | | ICAO1 |
| 2810 | IRHN | IRONHORSE TRANSPORTATION | | | SCAC4 |
| 2811 | IRHT | IRON HORSE TRANSPORT INC | | | SCAC4 |
| 2812 | IRHX | IRON HORSE RAILROAD | | | PWRC |
| 2813 | IRI | Navidtec | Callsign: Navid, | IR | AVCODES |
| 2814 | IRI | Navid | | | ICAO1 |
| 2815 | IRIPK | Instytut Rozwoju i Promocji Kolei | | PL | TRAFFIC |
| 2816 | IRIR | INTERPSPORT RACING INC | | | SCAC4 |
| 2817 | IRIS | Irisbus | City: Name of the Iveco buses in 1999 - 2013, due to merger with Renault Bus. | I | TRAFFIC |
| 2818 | IRIU | IRS INTERNATIONAL | | AUS | BIC |
| 2819 | IRIV | IRIS NAVIGATION LIMITED | | | SCAC4 |
| 2820 | IRJ | Bonyad Airlines | Callsign: Bonyad Air, | IR | AVCODES |
| 2821 | IRJ | Bonyad Airlines | | | ICAO1 |
| 2822 | IRK | Kish Air | IATA: Y9, Callsign: Kishair, IATA Prefix: 780, ICAO Designator changed to KIS. | IR | AVCODES |
| 2823 | IRK | Kish Air | IATA: Y9 | | ICAO1 |
| 2824 | IRKL | ISLANDER TRUCKING LLC | | | SCAC4 |
| 2825 | IRKU | LTD IRTEK | | RUS | BIC |
| 2826 | IRL | Irish Air Corps | Callsign: Irish, | IRL | AVCODES |
| 2827 | IRL | Irish Air Corps | | | ICAO1 |
| 2828 | IRLL | INNOVATIVE RESOURCES LLC | | | SCAC4 |
| 2829 | IRLO | IRIE LOGISTICS LLC | | | SCAC4 |
| 2830 | IRLQ | IRL | | | SCAC4 |
| 2831 | IRLS | INTERIOR LOGISTICS SERVICES LTD | | | SCAC4 |
| 2832 | IRLX | Western Railway Supply, Inc. | 7/2005 (not listed) | | NAKINA |
| 2833 | IRLX | WESTERN RAILROAD SUPPLY, INC. | | | PWRC |
| 2834 | IRLX | Western Railroad Supply | | | RSRV |
| 2835 | IRM | Mahan Airlines | IATA: W5, Callsign: Mahan Air, IATA Prefix: 537, Name changed to Mahan Air. | IR | AVCODES |
| 2836 | IRM | Mahan Air | IATA: W5, Callsign: Mahan Air, IATA Prefix: 537, Name changed from Mahan Airlines. | IR | AVCODES |
| 2837 | IRM | Mahan Air | IATA: W5 | | ICAO1 |
| 2838 | IRM | INDIANA RAILWAY MUSEUM | | | PWRC |
| 2839 | IRMC | IRION MACHINE LTD | | | SCAC4 |
| 2840 | IRMO | IRON MOUNTAIN CANADA CORPORATION | | | SCAC4 |
| 2841 | IRMR | Iron Ridge Railroad (Imagenary model railroad) | | USA | TRAFFIC |
| 2842 | IRMS | IVACO ROLLING MILLS 2004 LP | | | SCAC4 |
| 2843 | IRMT | INTERMODAL REPAIR MODIFICATION & TR | | | SCAC4 |
| 2844 | IRMX | III TRANSPORTATION | | | PWRC |
| 2845 | IRMZ | IOWA INTERSTATE RAILROAD, LTD. | | | PWRC |
| 2846 | IRMZ | III Transportation | | | RSRV |
| 2847 | IRN | Consolidated Rail Corp. | 1/1980-1/1994 | | NAKINA |
| 2848 | IRN | (The) Ironton R.R. Co. | 8/1920-10/1966 & 1/1975; eliminated 4/1976 | | NAKINA |
| 2849 | IRN | Ironton R.R. Co. | 4/38-10/66 & 1/75; eliminated 4/76 | | NRHS |
| 2850 | IRN | Consolidated Rail Corp. | 1/80-1/94 | | NRHS |
| 2851 | IRN | CONSOLIDATED RAIL CORP. [IRONTON RAILROAD] | | | PWRC |
| 2852 | IRN | Ironton Railroad (Conrail) | | | RSRV |
| 2853 | IRN | Illinois RailNet, Inc. | Real: IR | USA | TRAFFIC |
| 2854 | IRNB | IRONBOUND EXPRESS INC | | | SCAC4 |
| 2855 | IRNK | INTERNATIONAL RACK USA | | | SCAC4 |
| 2856 | IRNO | IRONHORSE TRANSPORT | | | SCAC4 |
| 2857 | IRNU | SEACUBE CONTAINERS LLC | | USA | BIC |
| 2858 | IRNU | Seacube Container Leasing | | | RSRV |
| 2859 | IRNU | SEACASTLE CONTAINER LEASING LLC | | | SCAC4 |
| 2860 | IRO | CSA Air, Inc. | Callsign: Iron Air, | USA | AVCODES |
| 2861 | IRO | CSA Air | | | ICAO1 |
| 2862 | IROD | REALCO SERVICES, INC./INTERNATIONAL | | | SCAC3 |
| 2863 | IROV | IRAN OVERLAND (MEDSPAN) | | | PWRC |
| 2864 | IRP | Payam (IPTAS) | IATA: 8P, Callsign: Payamair, Designator 8P* recalled by IATA | IR | AVCODES |
| 2865 | IRP | Payam (IPTAS) | IATA: 2F, Callsign: Payamair, Designator 8P* recalled by IATA | IR | AVCODES |
| 2866 | IRP | Payam Air | | | ICAO1 |
| 2867 | IRPA | INTER PACIFIC TRANSPORT | | | SCAC4 |
| 2868 | IRPX | Illinois River Packet Co. | 7/1923-7/1932 | | NAKINA |
| 2869 | IRPX | ILLINOIS RIVER PACKET CO. | | | PWRC |
| 2870 | IRQ | Qeshm Air | Callsign: Qeshm Air, ICAO Designator changed to QSM. | IR | AVCODES |
| 2871 | IRQ | Qeshm Air | | | ICAO1 |
| 2872 | IRQA | | | IRQ | TRAFFIC |
| 2873 | IRQS | IROQUOIS TRUCKING CO | | | SCAC1 |
| 2874 | IRQS | IROQUOIS TRUCKING CO INC | | | SCAC4 |
| 2875 | IRR | Tara Air Line | Callsign: Tarair, | IR | AVCODES |
| 2876 | IRR | Tara Air Line | | | ICAO1 |
| 2877 | IRR | Iraqi Republic Railways Establishment | | IQ | VKM |
| 2878 | IRRC | Iowa R.R. Co. | added 1/1982; eliminated 4/1988 | | NAKINA |
| 2879 | IRRC | Iowa R.R. Co. | added 1/82; eliminated 4/88 | | NRHS |
| 2880 | IRRC | IOWA RAILROAD CO. | | | PWRC |
| 2881 | IRRC | Iowa Railroad | | | RSRV |
| 2882 | IRRC | Iowa R.R. Co. | | USA | TRAFFIC |
| 2883 | IRRS | International Rail Road Systems, Inc. | 7/2000-7/2005 | | NAKINA |
| 2884 | IRRS | International Rail Road Systems, Inc. | Jul-00 | | NRHS |
| 2885 | IRRS | INTERNATIONAL RAIL ROAD SYSTEMS INC | | | PWRC |
| 2886 | IRRS | International Rail Road Systems | | | RSRV |
| 2887 | IRRS | INTERNATIONAL RAIL ROAD SYSTEMS INC | | | SCAC4 |
| 2888 | IRS | Sirius | Callsign: Sirius, | UA | AVCODES |
| 2889 | IRS | Sahand Airlines | Callsign: Sahand Air, | IR | AVCODES |
| 2890 | IRSC | INDY RAIL CAR SERVICE | | | PWRC |
| 2891 | IRSC | INTRANSIT CONTAINER INC | | | SCAC4 |
| 2892 | IRSI | INGRAM REFRIGERATED SERVICES INC | | | SCAC4 |
| 2893 | IRSI | International Rolling Stock Investment GmbH | | CH | TRAFFIC |
| 2894 | IRSIG | International Rolling Stock Investment GmbH | | CH | TRAFFIC |
| 2895 | IRSN | INTER RAIL SYSTEMS INC | | | SCAC4 |
| 2896 | IRSU | IZELAAR SALES BV | | | SCAC4 |
| 2897 | IRSX | TRANSPORTATION TECHNOLOGY CENTER IN | | | SCAC4 |
| 2898 | IRSY | INDUSTRIAL TRANSPORTATION SYSTEMS I | | | SCAC4 |
| 2899 | IRSZ | INTERPOOL RAIL SERVICES LTD. | | | PWRC |
| 2900 | IRSZ | Interpool Rail Services | | | RSRV |
