| 601 | UFEL | US FREIGHT EXPRESS LLC | | | SCAC4 |
| 602 | UFEQ | US FREIGHT EXPEDITORS CO INC | | | SCAC4 |
| 603 | UFFC | US FREIGHT FINDERS INC | | | SCAC4 |
| 604 | UFFI | UNITED FORCE FREIGHT INC | | | SCAC4 |
| 605 | UFFN | UNITED FREIGHT FORWARDERS INC | | | SCAC4 |
| 606 | UFFW | UNIVERSAL FREIGHT FORWARDERS LTD | | | SCAC4 |
| 607 | UFGC | US FREIGHT LLC | | | SCAC4 |
| 608 | UFGL | UNIFIED GLOBAL LOGISTICS INC | | | SCAC4 |
| 609 | UFGX | United Fuel Gas Co. | 8/1920-7/1923; 1/1952-7/1954; eliminated 10/1954 | | NAKINA |
| 610 | UFGX | United Fuel Gas Co. | Jan-52 | | NRHS |
| 611 | UFGX | UNITED FUEL GAS CO. | | | PWRC |
| 612 | UFHD | UNITED FISH DISTRIBUTORS INC | | | SCAC4 |
| 613 | UFHL | UPPAL FREIGHTS LTD | | | SCAC4 |
| 614 | UFI | Umbria Fly | Callsign: Umbria Fly, | I | AVCODES |
| 615 | UFIC | US FREIGHTWAYS INC | | | SCAC4 |
| 616 | UFIX | Utility Fuels, Inc. | added 7/1978; 1/1980-1/1994; eliminated 4/1994 | | NAKINA |
| 617 | UFIX | Houston Lighting & Power Co. | added 4/1994; eliminated 7/2000 | | NAKINA |
| 618 | UFIX | Reliant Energy HL&P | added 7/2000; 7/2000; eliminated 10/2004 | | NAKINA |
| 619 | UFIX | Texas Genco, LP | added 10/2004; eliminated 7/2005 | | NAKINA |
| 620 | UFIX | Texas Genco II, LP | added 7/2005; 7/2005; eliminated 10/2006 | | NAKINA |
| 621 | UFIX | NRG Energy, Inc. | added 10/2006; eliminated 4/2009; eliminated 7/2009 | | NAKINA |
| 622 | UFIX | Utility Fuels, Inc. | added 7/78; 1/80-1/94; eliminated 4/94 | | NRHS |
| 623 | UFIX | Houston Lighting & Power Co. | added 4/94; eliminated 7/2000 | | NRHS |
| 624 | UFIX | Reliant Energy HL&P | added 7/2000; 7/2000 | | NRHS |
| 625 | UFIX | *UTILITY FUELS INC. | | | PWRC |
| 626 | UFIX | +NRG ENERGY, INC. [TEXAS GENCO; [RELIANT ENERGY; HOUSTON LIGHTING & POWER COMPANY] | | | PWRC |
| 627 | UFIX | Utility Fuels | | | RSRV |
| 628 | UFIX | NRG ENERGY INC | | | SCAC4 |
| 629 | UFIZ | U.F.I. CORP | | | PWRC |
| 630 | UFL | Unifly | Callsign: Unifly, | GQ | AVCODES |
| 631 | UFLD | UNITED FLORAL DISTRIBUTORS | | | SCAC4 |
| 632 | UFLF | UNIQUE FREIGHT LINES INC | | | SCAC4 |
| 633 | UFLG | UNITED FREIGHT & LOGISTICS LTD | | | SCAC4 |
| 634 | UFLQ | UNITED FUEL LINES INC | | | SCAC4 |
| 635 | UFLR | UNITED FREIGHT LOGISTICS LLC | | | SCAC4 |
| 636 | UFLS | UF LOGISTICS INC | | | SCAC4 |
| 637 | UFO | Ateliers d\'Orval | | FR | VKM |
| 638 | UFOL | UNITED FUEL OIL | | | SCAC4 |
| 639 | UFPD | UNITED FRUIT & PRODUCE CO | | | SCAC4 |
| 640 | UFPM | UFP TRANSPORTATION INC | | | SCAC4 |
| 641 | UFPZ | UNIVERSAL FOREST PRODUCTS | | | PWRC |
| 642 | UFR | United Africa Airline (Liberia), Inc. | Callsign: United Africa, | LB | AVCODES |
| 643 | UFR | UNIFERTRANS S.A. | | RO | VKM |
| 644 | UFRE | U S FREIGHT INC | | | SCAC4 |
| 645 | UFRM | UNITED FARMERS COOPERATIVE | | | SCAC4 |
| 646 | UFRS | UNITED FREIGHT SERVICE INC | | | SCAC4 |
| 647 | UFS | UFS, Inc. | IATA: U2, Callsign: Feeder Flight, Founded in 1993. Ceased operations during 1999. | USA | AVCODES |
| 648 | UFS | UFS | | | ICAO1 |
| 649 | UFSI | UNIVERSAL FREIGHT SYSTEMS INC | | | SCAC4 |
| 650 | UFSK | US FREIGHT SYSTEMS INC | | | SCAC4 |
| 651 | UFSL | URBAN FREIGHT SERVICES LTD | | | SCAC4 |
| 652 | UFSP | UNLIMITED FURNITURE SUPPLY INC | | | SCAC4 |
| 653 | UFSQ | UNION FREIGHT SERVICES INC | | | SCAC4 |
| 654 | UFSS | CHIQUITA BRANDS, INC. | | | SCAC4 |
| 655 | UFSV | USA FREIGHT SERVICE INC | | | SCAC4 |
| 656 | UFSY | UNIVERSAL FREIGHT SYSTEM | | | SCAC4 |
| 657 | UFT | UniferTrans | | RO | TRAFFIC |
| 658 | UFTA | UNITED FREIGHT TRANSPORT LLC | | | SCAC4 |
| 659 | UFTI | UF TRUCKING INC | | | SCAC4 |
| 660 | UFTP | UNITED FREIGHT & TRANSPORT INC | | | SCAC4 |
| 661 | UFTQ | UNION FREIGHTWAYS, INC | | | SCAC1 |
| 662 | UFTQ | UNION FREIGHTWAYS CARRIERS LTD | | | SCAC4 |
| 663 | UFTU | UNIVERSAL FREIGHT CARRIERS, INC. | | | SCAC4 |
| 664 | UFTX | Residco | added 7/2008 | | NAKINA |
| 665 | UFTX | RESIDCO | | | PWRC |
| 666 | UFTX | RESIDCO | | | SCAC4 |
| 667 | UFXG | ULTRAFLEX AGENCY S A | | | SCAC4 |
| 668 | UG | Tuninter, S.A. | ICAO: TUI, IATA Prefix: 150, Name changed to Sevenair w.e.f. 07 July 2007. ICAO code SEN | TN | AVCODES |
| 669 | UG | Empresa (Aero Uruguay), S.A. | ICAO: AUO, Callsign: Uniform Oscar, Founded in 1977. Ceased operations in 2005. Designator recalled by IATA | ROU | AVCODES |
| 670 | UG | Uganda Aviation Services | Callsign: Ugandair, | EAU | AVCODES |
| 671 | UG | Sevenair | ICAO: SEN, Callsign: Sevair, IATA Prefix: 150, Name changed to Tunisair Express w.e.f. 14 January 2011. Name changed from Tuninter, S.A. w.e.f. 07 July 2007. | TN | AVCODES |
| 672 | UG | Tunisair Express | ICAO: TUX, Callsign: Tunexpress, IATA Prefix: 150, Name changed from Sevenair w.e.f. 14 January 2011 and previously from Tuninter, S.A. w.e.f. 07 July 2007. | TN | AVCODES |
| 673 | UGA | Uganda Airlines Corp. | IATA: QU, Callsign: Uganda, | EAU | AVCODES |
| 674 | UGA | Uganda Airlines Holdings Ltd. | IATA: QU, Callsign: Uganda, Name changed from Uganda Airlines Corp. Operations restarted. Ceased operations in October 2000 | EAU | AVCODES |
| 675 | UGA | Uganda Airlines Corp. | IATA: QU, Callsign: Uganda, Name changed to Uganda Airlines Holdings Ltd. Operations restarted. Ceased operations in October 2000 | EAU | AVCODES |
| 676 | UGA | Meridiana African Airlines (U) Limited d/b/a Air Uganda | IATA: U7, Callsign: Ugdana, IATA Prefix: 926, Founded in 2007. | EAU | AVCODES |
| 677 | UGA | Uganda Airlines | | | ICAO1 |
| 678 | UGAB | UNIVERSAL GEMS AND BEADS | | | SCAC4 |
| 679 | UGB | Meridiana Africa Airlines (U) Ltd | Callsign: Ugawings, | EAU | AVCODES |
| 680 | UGBL | UNIPACK GLOBAL RELOCATION INC | | | SCAC4 |
| 681 | UGC | Urgemer Canarias, S.L. | Callsign: Urgemer, | E | AVCODES |
| 682 | UGC | Urgemer Canarias | | | ICAO1 |
| 683 | UGCU | UNIPER GLOBAL COMMODITIES SE | | D | BIC |
| 684 | UGD | Uganda National Airlines Company Limited d/b/a/ Uganda Airlines | IATA: UR, Callsign: Crested, | EAU | AVCODES |
| 685 | UGEI | UNITED GROUP EXPRESS INC | | | SCAC4 |
| 686 | UGEZ | UNITED GRAIN ELEVATOR 2 | | | PWRC |
| 687 | UGFS | UNGER FREIGHT SERVICES INC | | | SCAC4 |
| 688 | UGII | UNITED GROUP INTERNATIONAL INC | | | SCAC4 |
| 689 | UGJ | UG Jet, s.r.o. | Callsign: Unijet, | CZ | AVCODES |
| 690 | UGJ | Uppsala - Gävle Järnväg | 1874 - 1933 | S | svenska-lok.se |
| 691 | UGL | Inter-Island Air, Inc. | Callsign: Ugly Van, | USA | AVCODES |
| 692 | UGL | Inter-Island Air | | | ICAO1 |
| 693 | UGLC | UNI GLOBAL LOGISTICS | | | SCAC4 |
| 694 | UGLF | USA GRANITE INC | | | SCAC4 |
| 695 | UGLI | UNION TRANSFER & STORAGE INC | | | SCAC4 |
| 696 | UGLK | USS GREAT LAKES LLC | | | SCAC4 |
| 697 | UGLL | UNITED GLOBAL LOGISTICS INC | | | SCAC4 |
| 698 | UGLP | UNICARGO GLOBAL LOGISTICS PRIVATE L | | | SCAC4 |
| 699 | UGLS | USA GLOBAL LOGISTICS LLC | | | SCAC4 |
| 700 | UGLT | UNITED GLOBAL TRANSPORT INC | | | SCAC4 |
