| 1 | UA | United Airlines, Inc. | ICAO: UAL, Callsign: United, IATA Prefix: 016, Name changed from United Air Lines, Inc. | USA | AVCODES |
| 2 | UA | Albatross Airlines | | AUS | AVCODES |
| 3 | UA | United Air Lines, Inc. | ICAO: UAL, Callsign: United, IATA Prefix: 016, Name changed to United Airlines, Inc. | USA | AVCODES |
| 4 | UA | United Airlines | | USA | TRAFFIC |
| 5 | UAA | UAS/AEF Leuchars | | GB | AVCODES |
| 6 | UAA | University Air Squadron | | | ICAO1 |
| 7 | UAAF | UNITED AIR LINES INC (AIR CODE UA) | | | SCAC4 |
| 8 | UAAI | UNITED ARAB AGENCIES INC | | | SCAC4 |
| 9 | UAAR | UNRAU, AARON | | | SCAC4 |
| 10 | UAAU | MOBIUS-GROUPPE EOOD | | BG | BIC |
| 11 | UAAX | American Acid Co. | 8/1920-7/1923 | | NAKINA |
| 12 | UAAX | AMERICAN ACID CO. | | | PWRC |
| 13 | UAB | United Arabian Airlines | Callsign: United Arabian, | SUD | AVCODES |
| 14 | UAB | United Arabian Airlines | | | ICAO1 |
| 15 | UABP | UAB Panevezio autobusu parkas | City: Panevezys | LT | TRAFFIC |
| 16 | UABS | UNITED ABACO SHIPPING | | | SCAC4 |
| 17 | UAC | United Air Charters | Callsign: Unitair, ICAO designator changed from UAC | ZW | AVCODES |
| 18 | UAC | United Air Charters | | | ICAO1 |
| 19 | UAC | UNITED AIRCRAFT CORP. | | | PWRC |
| 20 | UACB | UNIVERSAL AM-CAN LTD (BROKERAGE DIV | | | SCAC4 |
| 21 | UACL | UNIVERSAL AM-CAN, LTD | | | SCAC1 |
| 22 | UACL | UNIVERSAL AM-CAN LTD | | | SCAC4 |
| 23 | UACS | UNIVERSAL AM-CAN US | | | SCAC4 |
| 24 | UACU | HAPAG LLOYD A.G | | D | BIC |
| 25 | UACU | UNITED ARAB SHIPPERS | | | PWRC |
| 26 | UACU | United Arab Shipping | | | RSRV |
| 27 | UACU | UNITED ARAB SHIPPING CO SAG | | | SCAC4 |
| 28 | UACW | UNITED ARAB CHEMICAL CARRIERS LIMIT | | | SCAC4 |
| 29 | UACX | Universal Atlas Cement Co. | 7/1932; 1/1941-1/1952; eliminated 4/1953 | | NAKINA |
| 30 | UACX | Universal Atlas Cement Division of U.S. Steel Corp. | eliminated 7/1965 | | NAKINA |
| 31 | UACX | Universal Atlas Cement Co. | Jan-52 | | NRHS |
| 32 | UACX | Universal Atlas Cement Division of U.S. Steel Corp. | eliminated 7/65 | | NRHS |
| 33 | UACX | UNIVERSAL ATLAS CEMENT DIV., U.S. STEEL CORP. | | | PWRC |
| 34 | UAD | UAS/AEF Colerne | | GB | AVCODES |
| 35 | UAD | Univex Srl | | I | AVCODES |
| 36 | UAD | University Air Squadron | | | ICAO1 |
| 37 | UAE | Emirates | IATA: EK, Callsign: Emirates, IATA Prefix: 176, | UAE | AVCODES |
| 38 | UAE | Emirates Airline | IATA: EK | | ICAO1 |
| 39 | UAE | Emirates | | UAE | TRAFFIC |
| 40 | UAEA | United Aram Emirates Army | | UAE | TRAFFIC |
| 41 | UAEU | HAPAG LLOYD A.G | | D | BIC |
| 42 | UAEU | UNITED ARAB SHIPPING CO (S.A.G.) | | | PWRC |
| 43 | UAEU | United Arab Shipping | | | RSRV |
| 44 | UAEU | UNITED ARAB SHIPPING CO SAG | | | SCAC4 |
| 45 | UAF | United Arab Emirates Air Force | Callsign: Uniforce, | UAE | AVCODES |
| 46 | UAF | United Arab Emirates Air Force | | | ICAO1 |
| 47 | UAFU | UAFL UNITED AFRICA FEEDER LINE | | MUS | BIC |
| 48 | UAG | UAS/AEF Cambridge | | GB | AVCODES |
| 49 | UAG | AS Union Aviation | Callsign: Sakta, | LV | AVCODES |
| 50 | UAG | Afra Airlines | | | ICAO1 |
| 51 | UAH | UAS/AEF Newton | | GB | AVCODES |
| 52 | UAH | AEF Cranwell | | GB | AVCODES |
| 53 | UAH | University Air Squadron | | | ICAO1 |
| 54 | UAI | Union Africaine Des Transports | Callsign: Unair, | CI | AVCODES |
| 55 | UAI | Uni-Air International | Callsign: Uniair, | F | AVCODES |
| 56 | UAI | NIUAS/13 AEF | | GB | AVCODES |
| 57 | UAI | Union Africaine des Transports | | | ICAO1 |
| 58 | UAIN | UTILITY AVIATION, INC. | | | SCAC4 |
| 59 | UAIX | United Asphalts, Inc. | added 10/1992; 1/1994-7/2005; eliminated 1/2007 | | NAKINA |
| 60 | UAIX | United Asphalts, Inc. | added 10/92; 1/94-7/2000 | | NRHS |
| 61 | UAIX | UNITED ASPHALTS, INC. | | | PWRC |
| 62 | UAIX | United Asphalts | | | RSRV |
| 63 | UAIX | UNITED ASPHALTS, INC. | | | SCAC4 |
| 64 | UAJ | UAS/AEF Glasgow | | GB | AVCODES |
| 65 | UAJ | University Air Squadron | | | ICAO1 |
| 66 | UAK | Kiev Aviation Plant | Callsign: Aviation Plant, Ceased operations. | UA | AVCODES |
| 67 | UAK | Kiev Aviation Plant | | | ICAO1 |
| 68 | UAKU | ALARA LOGISTICS | | USA | BIC |
| 69 | UAL | United Airlines, Inc. | IATA: UA, Callsign: United, IATA Prefix: 016, Name changed from United Air Lines, Inc. | USA | AVCODES |
| 70 | UAL | United Air Lines, Inc. | IATA: UA, Callsign: United, IATA Prefix: 016, Name changed to United Airlines, Inc. | USA | AVCODES |
| 71 | UAL | United Airlines | IATA: UA | | ICAO1 |
| 72 | UALC | UNIVERSAL AFRICA LINES N V (N A) | | | SCAC4 |
| 73 | UALG | UNITED AMERICAN LOGISTICS INC | | | SCAC4 |
| 74 | UALL | UA LLC | | | SCAC4 |
| 75 | UALS | UAL UNIVERSAL AFRICA LINES N V (N A | | | SCAC4 |
| 76 | UAM | UAS/AEF Woodvale | | GB | AVCODES |
| 77 | UAME | URIAS ARELLANES, MARIA ELENA | | | SCAC4 |
| 78 | UAN | Aviaton | Callsign: Aviation, Ceased operations. | UA | AVCODES |
| 79 | UAO | UAS/AEF Benson | | GB | AVCODES |
| 80 | UAP | Antonov Airtracker | Callsign: Airtracker, Ceased operations. | UA | AVCODES |
| 81 | UAQ | UAS/AEF Leeming | | GB | AVCODES |
| 82 | UAR | Ukrainian Aviation Company "Aerostar" | Callsign: Aerostar, | UA | AVCODES |
| 83 | UAR | Uni-Air | | F | AVCODES |
| 84 | UAR | Aerostar Airlines | | | ICAO1 |
| 85 | UAS | UAS Cranwell | | GB | AVCODES |
| 86 | UAS | UAS/AEF Belfast | | GB | AVCODES |
| 87 | UASC | UNITED ARAB SHIPPING COMPANY | | | SCAC1 |
| 88 | UASI | UPS SCS (ASIA) LIMITED | | | SCAC4 |
| 89 | UASU | HAPAG LLOYD A.G | | D | BIC |
| 90 | UASU | UNITED ARAB SHIPPING COMPANY | | | PWRC |
| 91 | UASU | United Arab Shipping | | | RSRV |
| 92 | UASU | UNITED ARAB SHIPPING CO SAG | | | SCAC4 |
| 93 | UASV | UTKILEN AS | | | SCAC4 |
| 94 | UASW | UNIFIED AIRCRAFT SERVICES INC | | | SCAC4 |
| 95 | UASX | United Alloy Steel Corp. | 7/1923 | | NAKINA |
| 96 | UASX | UNITED ALLOY STEEL CORP. | | | PWRC |
| 97 | UASZ | UNITED ARAB SHIPPERS | | | PWRC |
| 98 | UASZ | United Arab Shipping | | | RSRV |
| 99 | UASZ | UNITED ARAB SHIPPERS | | | SCAC4 |
| 100 | UAT | Universal Air Transport | Callsign: Riverside, | GB | AVCODES |
