| 2701 | IPUS | IMPRINT PLUS | | | SCAC4 |
| 2702 | IPWX | Alliant Energy | added 4/2000; 7/2000-7/2005 | | NAKINA |
| 2703 | IPWX | Interstate Power Co. | added 7/1979; 1/1980-1/1994; eliminated 4/2000 | | NAKINA |
| 2704 | IPWX | Alliant Energy | added 4/2000; 7/2000 | | NRHS |
| 2705 | IPWX | Interstate Power Co. | added 7/79; 1/80-1/94; eliminated 4/2000 | | NRHS |
| 2706 | IPWX | ALLIANT ENERGY [INTERSTATE POWER COMPANY] | | | PWRC |
| 2707 | IPWX | Interstate Power (Alliant Energy) | | | RSRV |
| 2708 | IPWX | ALLIANT ENERGY | | | SCAC4 |
| 2709 | IPX | International Parcel Express, Inc. | Callsign: Speed Pack, | USA | AVCODES |
| 2710 | IPXE | INTERNATIONAL PAPER (XPEDX- ALABAMA | | | SCAC4 |
| 2711 | IPXI | INTER PACIFIC EXPRESS INC | | | SCAC4 |
| 2712 | IPXQ | ITP EXPRESS INC | | | SCAC4 |
| 2713 | IPXU | SEACUBE CONTAINERS LLC | | USA | BIC |
| 2714 | IPXU | Seacube Container Leasing | | | RSRV |
| 2715 | IPXU | INTERPOOL LTD | | | SCAC4 |
| 2716 | IPZ | INTALCO PLANT | | | PWRC |
| 2717 | IPZ | IPZ GmbH | | DE | VKM |
| 2718 | IQ | Augsburg Airways GmbH | ICAO: AUB, Callsign: Augsburg Air, IATA Prefix: 614, Ceased operations on 31 October 2013. Founded in 1980 as Interot Airways. | D | AVCODES |
| 2719 | IQ | Interot Airways | ICAO: IRT, Callsign: Interot, IATA Prefix: 614, Name changed to Augsbury-Airways GmbH. Founded in 1980. | D | AVCODES |
| 2720 | IQ | Caribbean Airways Ltd. | ICAO: IQQ, Callsign: Caribjet, Name changed from International Caribbean Airline | BDS | AVCODES |
| 2721 | IQ | International Caribbean Airline | Name changed to Caribbean Airways Ltd. | BDS | AVCODES |
| 2722 | IQ | Qazaq Air Joint Stock Company | ICAO: QAZ, Callsign: Samruk, | KZ | AVCODES |
| 2723 | IQAA | IROQUOIS IRONWORKER INC | | | SCAC4 |
| 2724 | IQAF | Iraqi Air Force | | IRQ | TRAFFIC |
| 2725 | IQAO | INIGUEZ QUINONEZ, ARMANDO | | | SCAC4 |
| 2726 | IQCK | INTELLIQUICK DELIVERY INC | | | SCAC4 |
| 2727 | IQIX | Industria Quimica Del Istmo S.A. de C.V. | added 7/2000; 7/2000-7/2005 | | NAKINA |
| 2728 | IQIX | Industria Quimica Del Istmo S.A. de C.V. | added 7/2000; 7/2000 | | NRHS |
| 2729 | IQIX | INDUSTRIA QUIMICA DEL ISTMO SA DE CV | | | PWRC |
| 2730 | IQIX | Industria Quimica Del letmo de CV | | | RSRV |
| 2731 | IQLE | INTERNATIONAL EXPRESS | | | SCAC4 |
| 2732 | IQP | Happy Landings (Flight Training) | Callsign: Iqra Pakistan, | PK | AVCODES |
| 2733 | IQQ | Caribbean Airways Ltd. | Callsign: Caribjet, | BDS | AVCODES |
| 2734 | IQQ | Caribbean Airways Ltd. | IATA: IQ, Callsign: Caribjet, Name changed from International Caribbean Airline | BDS | AVCODES |
| 2735 | IQQ | Caribbean Airways | | | ICAO1 |
| 2736 | 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 |
| 2737 | IR | Illinois RailNet, Inc. | 7/2000-7/2005 | | NAKINA |
| 2738 | IR | Illinois RailNet, Inc. | Jul-00 | | NRHS |
| 2739 | IR | ILLINOIS RAILNET INC. | | | PWRC |
| 2740 | IR | Illinois RailNet | | | RSRV |
| 2741 | IR | ILLINOIS RAILNET INC | | | SCAC4 |
| 2742 | IR | | | IL | TRAFFIC |
| 2743 | IR | Indian Railways | | IN | VKM |
| 2744 | 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 |
| 2745 | IRA | Iran Air | IATA: IR | | ICAO1 |
| 2746 | IRA | Iran Air | | IR | TRAFFIC |
| 2747 | IRAIL | Independent Railways of Australia Pts. | | AUS | TRAFFIC |
| 2748 | IRAT | IDAHOROADS INC | | | SCAC4 |
| 2749 | IRB | Iran Air Tours Co. | IATA: B9, IATA Prefix: 491, Name changed to Iran Airtour Airline. Desigantor B9 reinstated by IATA | IR | AVCODES |
| 2750 | IRB | Iran Airtour Airline | IATA: B9, IATA Prefix: 491, Name changed to Iran Air Tours Co. Desigantor B9 reinstated by IATA | IR | AVCODES |
| 2751 | IRB | Iranair Tours | | | ICAO1 |
| 2752 | IRBD | IRONBOUND TRANSPORT | | | SCAC4 |
| 2753 | IRBL | INTEGRA FARMS LTD | | | SCAC4 |
| 2754 | IRBY | IRBY WAYNE OIL COMPANY | | | SCAC4 |
| 2755 | IRC | Iran Asseman Airlines | IATA: EP, IATA Prefix: 815, Name changed to Iran Aseman Airlines | IR | AVCODES |
| 2756 | IRC | Iran Aseman Airline | IATA: EP, Callsign: Aseman, IATA Prefix: 815, Name changed from Iran Asseman Airlines | IR | AVCODES |
| 2757 | IRC | Iran Aseman Airlines | IATA: EP | | ICAO1 |
| 2758 | IRC | Intercolonial Ry. of Canada (Canadian National Rys.) | 8/1920-7/1932 | | NAKINA |
| 2759 | IRC | Canadian Government Rys. (Canadian National Rys.) | 8/1920-7/1932 | | NAKINA |
| 2760 | IRC | Canadian Government Rys. (Canadian National Rys.) | 23-Jul | | NRHS |
| 2761 | IRC | CANADIAN NATIONAL RWY. [INTERCOLONIAL RWY. OF CANADA] | | | PWRC |
| 2762 | IRC | InterRegional Calatori | | RO | TRAFFIC |
| 2763 | IRCC | INDIAN RIVER CONSTRUCTION CO | | | PWRC |
| 2764 | IRCH | INTERNATIONAL PAPER (LAFAYETTE CONT | | | SCAC4 |
| 2765 | IRCL | INDUSTRIAL RESIN RECYCLING INC | | | SCAC4 |
| 2766 | IRCN | IROC TRANSPORT INC | | | SCAC4 |
| 2767 | IRCU | INTRUSCO LLC | | RUS | BIC |
| 2768 | IRCU | KRONOS SA | | | SCAC4 |
| 2769 | IRCX | Island Creek Corp. | eliminated 7/1997 | | NAKINA |
| 2770 | IRCX | Nationwide Railroad Leasing, Inc. | added 4/1966; 10/1966-4/1970; eliminated 1/1971 | | NAKINA |
| 2771 | IRCX | Morrison Plan, Inc. | added 1/1962; 7/1965; eliminated 4/1966 | | NAKINA |
| 2772 | IRCX | International Railway Car Leasing Co. | added 1/1959; 4/1961; eliminated 1/1962 | | NAKINA |
| 2773 | IRCX | International Railway Car Co. | added 10/1954; 10/1957; eliminated 1/1959 | | NAKINA |
| 2774 | IRCX | International Railway Car & Equipment Co. | 1/1945-7/1954 (not listed) | | NAKINA |
| 2775 | IRCX | Indian Refining Co., Inc. | 8/1920-7/1932 | | NAKINA |
| 2776 | IRCX | International Railway Car & Equipment Co. | Jan-52 | | NRHS |
| 2777 | IRCX | International Railway Car Co. | 10/57; eliminated 1/59 | | NRHS |
| 2778 | IRCX | International Railway Car Leasing Co. | added 1/59; 4/61; eliminated 1/62 | | NRHS |
| 2779 | IRCX | Morrison Plan, Inc. | added 1/62; 7/65; eliminated 4/66 | | NRHS |
| 2780 | IRCX | Nationwide Railroad Leasing, Inc. | added 4/66; 10/66-4/70; eliminated 1/71 | | NRHS |
| 2781 | IRCX | Island Creek Corp. | eliminated 7/97 | | NRHS |
| 2782 | IRCX | *INDIAN REFINING CO., INC. | | | PWRC |
| 2783 | IRCX | *NATIONWIDE RAILROAD LEASING, INC. [MORRISON PLAN, INC.; INTERNATIONAL RAILWAY CAR LEASING CO.] | | | PWRC |
| 2784 | IRCX | *RETIRED 08-15-91 ATP (0359) | | | PWRC |
| 2785 | IRCX | *ISLAND CREEK CORP. | | | PWRC |
| 2786 | IRCZ | ITEL RAIL CORPORATION | | | PWRC |
| 2787 | IRD | Arvand Airlines | Callsign: Arvand, | IR | AVCODES |
| 2788 | IRD | Arvand Airlines | | | ICAO1 |
| 2789 | IRDI | INTEGRITY RETAIL DISTRIBUTION INC | | | SCAC4 |
| 2790 | IRE | Pariz Air | Callsign: Parizair, | IR | AVCODES |
| 2791 | IRE | Pariz Air | | | ICAO1 |
| 2792 | IREB | IRELAND, ROBERT TRUCKING | | | SCAC4 |
| 2793 | IREL | IRELAND, S D CONCRETE | | | SCAC4 |
| 2794 | IRES | IRI TRUCKING | | | SCAC4 |
| 2795 | IREX | IRECO, Inc. | added 10/1986; eliminated 1/1994; 1/1994-7/2005 (not listed) | | NAKINA |
| 2796 | IREX | Indianapolis Refrigerator Express (Indianapolis Abbatoir Co.) | 8/1920-7/1930 | | NAKINA |
| 2797 | IREX | IRECO, Inc. | added 10/86; eliminated 1/94; 7/2000 | | NRHS |
| 2798 | IREX | *INDIANAPOLIS ABBATOIR CO. (INDIANAPOLIS REFRIGERATOR EXPRESS) | | | PWRC |
| 2799 | IREX | *DYNO NOBEL, INC. | | | PWRC |
| 2800 | IREX | +IRECO INC. [ILLINOIS RAILWAY EQUIPMENT CO.] | | | PWRC |
