| 701 | UGLU | UNIGLOBAL SHIPPING COMPANY LIMITED | | HK | BIC |
| 702 | UGLW | UNITED GROUP LOGISTICS UGL | | | SCAC4 |
| 703 | UGMA | U GET MOORE EXPRESS INC | | | SCAC4 |
| 704 | UGMT | U G M TRANSPORT INC | | | SCAC4 |
| 705 | UGMU | GREENCOMPASS MARINE S.A. | | PA | BIC |
| 706 | UGMU | EVERGREEN INTERNATIONAL (USA) CORPORATION | | | PWRC |
| 707 | UGMU | Evergreen International (Greencompass Marine) | | | RSRV |
| 708 | UGMU | UNIGLORY MARINE CORP | | | SCAC4 |
| 709 | UGN | Yuzhnaya Aircompany | Callsign: Pluton, | KZ | AVCODES |
| 710 | UGN | Yuzhnaya Aircompany | | | ICAO1 |
| 711 | UGNC | UGLEM NESS CO INC | | | SCAC4 |
| 712 | UGNY | UNITED GLOBAL SERVICES (NY) CORP | | | SCAC4 |
| 713 | UGP | Shar Ink Ltd. | Callsign: Sharnik, | RUS | AVCODES |
| 714 | UGP | Shar Ink | | | ICAO1 |
| 715 | UGPU | ROZA MIRA LLC | | RUS | BIC |
| 716 | UGPX | United Gas Pipe Line Co. | 4/1938-1/1943 | | NAKINA |
| 717 | UGPX | United Gas Pipe Line Co. | Apr-38 | | NRHS |
| 718 | UGPX | UNITED GAS PIPE LINE CO. | | | PWRC |
| 719 | UGRD | UNION GANADERA REGIONAL DE COAHUILA | | | SCAC4 |
| 720 | UGS | SKA Air and Logistics (Uganda) Limited | Callsign: Sky Uganda, | EAU | AVCODES |
| 721 | UGSU | UCAK SHIPPING CORP | | PA | BIC |
| 722 | UGSX | United Gas Public Service Co. | 7/1932-7/1937 | | NAKINA |
| 723 | UGSX | UNITED GAS PUBLIC SERVICE CO. | | | PWRC |
| 724 | UGTI | UNGER TRANSPORT INC | | | SCAC4 |
| 725 | UGTU | BOECKMANS N V | | | SCAC4 |
| 726 | UGX | East Afrian Airlines Limited | IATA: QU, Callsign: Crane, IATA designator changed from QU* | EAU | AVCODES |
| 727 | UGX | East Afrian Airlines Limited | IATA: QU, Callsign: Crane, IATA designator changed to QU | EAU | AVCODES |
| 728 | UGX | East Afrian Airlines Limited | Callsign: Crane, Designator QU* recalled by IATA. | EAU | AVCODES |
| 729 | UGX | East African | IATA: QU | | ICAO1 |
| 730 | UH | Eurasia Aircompany, JSC | ICAO: EUS, Callsign: Eurasia, IATA Prefix: 914, | RUS | AVCODES |
| 731 | UH | Bristow Helicopters Group Ltd. | ICAO: BHL, Callsign: Bristow, Desigantor UH recalled by IATA | GB | AVCODES |
| 732 | UH | U.S. Helicopter Corporation | ICAO: USH, Callsign: US Heli, Founded in 2004. Ceased operations on 25 September 2009. | USA | AVCODES |
| 733 | UH | AtlasJet Ukraine | ICAO: UJX, Callsign: Atlas Ukraine, IATA Prefix: 500, Ceased operations. | UA | AVCODES |
| 734 | UH | Jet Exchange Limited | ICAO: XCH, Callsign: Exchange, | GB | AVCODES |
| 735 | UHAM | UNIVERSAL HANDLING EQUIPMENT COMPAN | | | SCAC4 |
| 736 | UHC | Ukrainian Handling Company LLC | Callsign: Handling Company, | UA | AVCODES |
| 737 | UHCA | UNITED HAULING CORP | | | SCAC4 |
| 738 | UHE | Unidad de Helicopteros de la Ertzaintza | | E | AVCODES |
| 739 | UHER | UHER TRUCKING INC | | | SCAC4 |
| 740 | UHI | Unicorn Air Charter Services | | GH | AVCODES |
| 741 | UHIG | UNITED HIGHWAYS INC | | | SCAC4 |
| 742 | UHJF | UTAH STEP SAVER | | | SCAC4 |
| 743 | UHL | Ukrainian Helicopters, CJS Company | Callsign: Ukraine Copters, Name changed to Aviation Company Ukrainian Helicopters. | UA | AVCODES |
| 744 | UHL | Aviation Company Ukrainian Helicopters | Callsign: Ukraine Copters, Name changed from Ukrainian Helicopters, CJS Company. | UA | AVCODES |
| 745 | UHL | Ukrainian Helicopters | | | ICAO1 |
| 746 | UHL | G.Uhlmann GmbH | | DE | VKM |
| 747 | UHLG | UHU TRUCKING | | | SCAC4 |
| 748 | UHLH | UNITED HEIRS LLC | | | SCAC4 |
| 749 | UHLI | UHLIK TRANSPORT INC | | | SCAC4 |
| 750 | UHLU | UNIT HIRE LIMITED | | GB | BIC |
| 751 | UHMU | HIMMAGISTRAL LTD | | RUS | BIC |
| 752 | UHO | LLC H3Operations | Callsign: Heliops, | UA | AVCODES |
| 753 | UHP | United Air Service | Callsign: Sierra Yankee, Designator SY recalled by IATA | WAN | AVCODES |
| 754 | UHP | United Air Service | IATA: SY, Callsign: Sierra Yankee, Designator SY recalled by IATA | WAN | AVCODES |
| 755 | UHRX | Upper Hudson River R.R. Corp. | 7/2000 (not listed); added 1/2003; eliminated 4/2003; 7/2005 (not listed) | | NAKINA |
| 756 | UHRX | Upper Hudson River R.R. Corp. | Jul-00 | | NRHS |
| 757 | UHRX | UPPER HUDSON RIVER RAILROAD | | | PWRC |
| 758 | UHRX | Upper Hudson River Railroad | | | RSRV |
| 759 | UHRX | UPPER HUDSON RIVER RAILROAD CORPORA | | | SCAC4 |
| 760 | UHS | Ulyanovsk Higher Civil Aviation School | Callsign: Pilot Air, | RUS | AVCODES |
| 761 | UHS | Ulyanovsk Higher Civil Aviation School | | | ICAO1 |
| 762 | UHSL | ULTRA HIGH SPECIALTIES LLC | | | SCAC4 |
| 763 | UI | Eurocypria Airlines Ltd. | ICAO: ECA, Callsign: Eurocypria, IATA Prefix: 475, Liquidated on 29 November 2010 after EU failed to approve merger with Cyprus Airways | CY | AVCODES |
| 764 | UI | Alaska Seaplane Service, L.L.C. | IATA Designator changed to J5 | USA | AVCODES |
| 765 | UI | Société de Transport Aerien du Rwanda (STAR) | Callsign: Star, | RWA | AVCODES |
| 766 | UI | Cool Tours d/b/a San Juan Aviation | IATA Designator changed to JI | PRI | AVCODES |
| 767 | UI | Auric Air Services Limited | ICAO: AUK, Callsign: Auric Services, | EAT | AVCODES |
| 768 | UI | Ultimate Jetcharters, Inc. | ICAO: UJC, Callsign: Ultimate, IATA designator changed to UE. | USA | AVCODES |
| 769 | UIA | UNI Airways Corporation | IATA: B7, Callsign: Glory, IATA Prefix: 525, | RC | AVCODES |
| 770 | UIA | Uni Air | | RC | TRAFFIC |
| 771 | UIAW | UIA WORLDWIDE LOGISTICS INC | | | SCAC4 |
| 772 | UIBU | UNION INTERNATIONAL BITUMEN FACTORY | | | SCAC4 |
| 773 | UIC | Utah Idaho Central R.R. Co. | 7/1923-7/1936 | | NAKINA |
| 774 | UIC | Utah Idaho Central R.R. | 4/1938-7/1954 | | NAKINA |
| 775 | UIC | Utah Idaho Central R.R. | 4/38-1/52 | | NRHS |
| 776 | UIC | *UTAH IDAHO CENTRAL RAILROAD CO. | | | PWRC |
| 777 | UIC | *MARCHEM LTD | | | PWRC |
| 778 | UICC | UNITED INDUSTRIAL SERVICES | | | SCAC4 |
| 779 | UICO | UNITED BRIDGE TRANSPORTATION LLC | | | SCAC4 |
| 780 | UICQ | UNDERWOOD INDUSTRIAL CONTRACTORS IN | | | SCAC4 |
| 781 | UIDS | UNITED STATIONERS SUPPLY CO | | | SCAC4 |
| 782 | UIET | UNITED TRANSPORT LLC | | | SCAC4 |
| 783 | UIFU | UNITEX INTERNATIONAL FORWARDING (HK) LTD | | HK | BIC |
| 784 | UIID | UNICORN INDUSTRIES INC | | | SCAC4 |
| 785 | UIIN | US INTERMODAL INC | | | SCAC4 |
| 786 | UILC | UNITED INTERMODAL LLC | | | SCAC4 |
| 787 | UIME | U & I MOVERS EXPRESS | | | SCAC4 |
| 788 | UIMW | UNITED INTERNATIONAL MANAGEMENT LTD | | | SCAC4 |
| 789 | UIMX | United Iron & Metal LLC | 7/2005 (not listed) | | NAKINA |
| 790 | UIMX | UNITED IRON & METAL LLC | | | PWRC |
| 791 | UIMX | UNITED IRON & METAL LLC | | | SCAC4 |
| 792 | UINC | UNICOVER INC | | | SCAC4 |
| 793 | UINL | UNITRANS INTERNATIONAL INC | | | SCAC4 |
| 794 | UINR | UNITRANS INC | | | SCAC4 |
| 795 | UIQC | UNIVERSAL CARGO MANAGEMENT INC | | | SCAC4 |
| 796 | UIR | Ukrair, Aviacompany Ltd. | Callsign: Ukrair, Ceased operations. | UA | AVCODES |
| 797 | UISI | UNITED INDUSTRIAL SUPPLY (1985) INC | | | SCAC4 |
| 798 | UISN | UIS TRANSPORTATION INC | | | SCAC4 |
| 799 | UISZ | USCO UNDUSTRY SASKATHEWAN | | | PWRC |
| 800 | UIT | Universitetet I Tromso | Callsign: Spirit, ICAO Callsign changed to Artic. | N | AVCODES |
