| 101 | UAL | United Airlines | IATA: UA | | ICAO1 |
| 102 | UALC | UNIVERSAL AFRICA LINES N V (N A) | | | SCAC4 |
| 103 | UALG | UNITED AMERICAN LOGISTICS INC | | | SCAC4 |
| 104 | UALL | UA LLC | | | SCAC4 |
| 105 | UALS | UAL UNIVERSAL AFRICA LINES N V (N A | | | SCAC4 |
| 106 | UAM | UAS/AEF Woodvale | | GB | AVCODES |
| 107 | UAME | URIAS ARELLANES, MARIA ELENA | | | SCAC4 |
| 108 | UAN | Aviaton | Callsign: Aviation, Ceased operations. | UA | AVCODES |
| 109 | UAO | UAS/AEF Benson | | GB | AVCODES |
| 110 | UAP | Antonov Airtracker | Callsign: Airtracker, Ceased operations. | UA | AVCODES |
| 111 | UAQ | UAS/AEF Leeming | | GB | AVCODES |
| 112 | UAR | Ukrainian Aviation Company "Aerostar" | Callsign: Aerostar, | UA | AVCODES |
| 113 | UAR | Uni-Air | | F | AVCODES |
| 114 | UAR | Aerostar Airlines | | | ICAO1 |
| 115 | UAS | UAS Cranwell | | GB | AVCODES |
| 116 | UAS | UAS/AEF Belfast | | GB | AVCODES |
| 117 | UASC | UNITED ARAB SHIPPING COMPANY | | | SCAC1 |
| 118 | UASI | UPS SCS (ASIA) LIMITED | | | SCAC4 |
| 119 | UASU | HAPAG LLOYD A.G | | D | BIC |
| 120 | UASU | UNITED ARAB SHIPPING COMPANY | | | PWRC |
| 121 | UASU | United Arab Shipping | | | RSRV |
| 122 | UASU | UNITED ARAB SHIPPING CO SAG | | | SCAC4 |
| 123 | UASV | UTKILEN AS | | | SCAC4 |
| 124 | UASW | UNIFIED AIRCRAFT SERVICES INC | | | SCAC4 |
| 125 | UASX | United Alloy Steel Corp. | 7/1923 | | NAKINA |
| 126 | UASX | UNITED ALLOY STEEL CORP. | | | PWRC |
| 127 | UASZ | UNITED ARAB SHIPPERS | | | PWRC |
| 128 | UASZ | United Arab Shipping | | | RSRV |
| 129 | UASZ | UNITED ARAB SHIPPERS | | | SCAC4 |
| 130 | UAT | Universal Air Transport | Callsign: Riverside, | GB | AVCODES |
| 131 | UAT | UZ Aero Tech Group | Callsign: Uztech, | UZ | AVCODES |
| 132 | UATA | UA AUTO TRANSPORT INC | | | SCAC4 |
| 133 | UATN | UA TRANSPORTATION | | | SCAC4 |
| 134 | UAU | UAS/AEF Boscombe Down | Callsign: Uniform, | GB | AVCODES |
| 135 | UAUS | UNITED AUTOSPORTS USA LLC | | | SCAC4 |
| 136 | UAV | UAS / AEF Wyton | | GB | AVCODES |
| 137 | UAW | UAS/AEF St Athan | | GB | AVCODES |
| 138 | UAWX | Union Acid Works, Inc. (Standard Wholesale Phosphate & Acid Works, Inc.) | 7/1930-7/1935 | | NAKINA |
| 139 | UAWX | Standard Wholesale Phosphate & Acid Works, Inc. | 7/1937-4/1947 | | NAKINA |
| 140 | UAWX | Mathieson Chemical Corp. | 1/1950 (not listed) | | NAKINA |
| 141 | UAWX | Union Acid Works, Inc. (Standard Wholesale Phosphate & Acid Works, Inc.) | Apr-38 | | NRHS |
| 142 | UAWX | *STANDARD WHOLESALE PHOSPHATE & ACID WORKS, INC. [UNION ACID WORKS, INC.] | | | PWRC |
| 143 | UAWX | *MATHIESON CHEMICAL CORP. | | | PWRC |
| 144 | UAX | UAS/AEF Church Fenton | | GB | AVCODES |
| 145 | UAY | UAS/AEF Cosford | | GB | AVCODES |
| 146 | UB | Myanmar Airways | ICAO: UBA, Callsign: Unionair, IATA Prefix: 209, Name changed to Myanmar National Airlines | MYA | AVCODES |
| 147 | UB | Union of Burma Airways | Callsign: Uionair, | MYA | AVCODES |
| 148 | UB | Burma Airways Corporation | Callsign: Uion Air, | MYA | AVCODES |
| 149 | UB | Air Cargo Global s.r.o. | ICAO: CCC, Callsign: Global Cargo, IATA Prefix: 159, IATA Designator changed to CW. | SK | AVCODES |
| 150 | UB | Myanmar National Airlines | ICAO: UBA, Callsign: Unionair, Name changed from Myanmar Airways | MYA | AVCODES |
| 151 | UB | UNION BELT OF DETROIT | | | PWRC |
| 152 | UBA | Myanmar Airways | IATA: UB, Callsign: Unionair, IATA Prefix: 209, Name changed to Myanmar National Airlines | MYA | AVCODES |
| 153 | UBA | Myanmar National Airlines | IATA: UB, Callsign: Unionair, Name changed from Myanmar Airways | MYA | AVCODES |
| 154 | UBA | Myanma Airways | IATA: UB | | ICAO1 |
| 155 | UBAI | URBANO INTERNATIONAL INC | | | SCAC4 |
| 156 | UBB | Usedomer Bäderbahn GmbH | Heringsdorf | D | privat-bahn.de |
| 157 | UBB | Usedomer Bäder-Bahn | | D | TRAFFIC |
| 158 | UBB | Usedomer Bäder-Bahn | | DE | VKM |
| 159 | UBBU | DEN HARTOGH DRY BULK LOGISTICS LTD | | GB | BIC |
| 160 | UBBU | U B C LTD | | | SCAC4 |
| 161 | UBCA | UNITED BULK CARRIERS (USA) | | | SCAC4 |
| 162 | UBCI | UNITED BULK CARRIERS INTERNATIONAL | | | SCAC4 |
| 163 | UBCL | USA BOUQUET COMPANY LLC | | | SCAC4 |
| 164 | UBCM | UNITED BULK CARRIERS INTERNATIONAL | | | SCAC4 |
| 165 | UBCU | UNITED FRUIT CO. | | | PWRC |
| 166 | UBCU | United Fruit | | | RSRV |
| 167 | UBCU | CHIQUITA BRANDS (GREAT WHITE FLEET) | | | SCAC1 |
| 168 | UBCU | UNITED FRUIT CO (CHIQUITA BRANDS IN | | | SCAC4 |
| 169 | UBD | United Airways Bangladesh Ltd | IATA: 4H, Callsign: United Bangladesh, Founded in 2005. Commenced operations on 10 July 2007. Ceased operations on 06 March 2016. | BD | AVCODES |
| 170 | UBD | UR Airlines d/b/a UBD | IATA: UD, Callsign: Urair, All flights operated by Aircompany Jonika LLC. (JNK) | IRQ | AVCODES |
| 171 | UBDI | UB DISTRIBUTORS LLC | | | SCAC4 |
| 172 | UBE | Limited Liability Company Bees Airline | IATA: 7B, Callsign: Flower Bee, IATA Prefix: 517, | UA | AVCODES |
| 173 | UBEI | US BLUE EXPRESS INC | | | SCAC4 |
| 174 | UBEX | United Bio Energy Ingredients, LLC | 7/2005 (not listed) | | NAKINA |
| 175 | UBEX | UNITED BIO ENERGY INGREDIENTS, LLC | | | PWRC |
| 176 | UBFL | UNITED - BUCKINGHAM FRT LINES | | | PWRC |
| 177 | UBFS | URBAN FREIGHT SERVICES | | | SCAC4 |
| 178 | UBG | US-Bangla Airlines Limited | IATA: BS, Callsign: Banglastar, Founded in 2013. Commenced operations on 17 July 2014. | BD | AVCODES |
| 179 | UBKI | UB TRUCKING INC | | | SCAC4 |
| 180 | UBLA | UNIQUE BROKERAGE & LOGISTICS INC | | | SCAC4 |
| 181 | UBLG | USA BORDER LOGISTICS LLC | | | SCAC4 |
| 182 | UBLT | UNIBILT TRANSPORT INC | | | SCAC4 |
| 183 | UBMU | UNITED BALTIC CORP. LTD. | | | PWRC |
| 184 | UBMU | United Baltic Corporation Limited | | | RSRV |
| 185 | UBRG | UTS BROKERAGE | | | SCAC4 |
| 186 | UBRL | UGLAND BROTHERS LIMITED | | | SCAC4 |
| 187 | UBROS | United Brothers | | USA | TRAFFIC |
| 188 | UBRS | UB RESOURCES | | | SCAC4 |
| 189 | UBRV | UNCLE BOBS RV | | | SCAC4 |
| 190 | UBS | Barbedos Aviation Services Limited | Callsign: Barbedos, | WAN | AVCODES |
| 191 | UBSC | US BLUE STAR CO | | | SCAC4 |
| 192 | UBSL | UNIVERSAL BUILDING SOLUTIONS LTD | | | SCAC4 |
| 193 | UBT | Norse Atlantic UK Limited | IATA: Z0, Callsign: Longboat, IATA Prefix: 536, Subsidiary of Norse Atlantic Airways AS. AOC grant 23 September 2022. | GB | AVCODES |
| 194 | UBTA | UGLAND BULK TRANSPORT A/S | | | SCAC4 |
| 195 | UBTE | UTLEY, BRENT TRUCKING | | | SCAC4 |
| 196 | UBTK | US BOND TRUCKING INC | | | SCAC4 |
| 197 | UBTN | URBAN TANKER CORPORATION | | | SCAC4 |
| 198 | UBTO | UNITED BRIDGE TRUCKING CORP | | | SCAC4 |
| 199 | UBTT | UNCLE BEN TRANSPORT INC | | | SCAC4 |
| 200 | UBTX | Union Bag & Paper Corp. | added 7/1955; eliminated 10/1956 | | NAKINA |
