| 1 | UR | Brintel Helicopters t/a British International Helicopters Ltd. | ICAO: BIH, Callsign: Lion, ICAO Callsign changed to Brintel | GB | AVCODES |
| 2 | UR | Brintel Helicopters t/a British International Helicopters Ltd. | ICAO: BIH, Callsign: Brintel, Merged with Bond / New name Scotia Helicopter Service | GB | AVCODES |
| 3 | UR | British Airways Helicopters Ltd. | ICAO: BIH, Renamed British International Helicopters Ltd. | GB | AVCODES |
| 4 | UR | British International Helicopters Ltd. | ICAO: BIH, Callsign: Lion, IATA designator changed to BS* | GB | AVCODES |
| 5 | UR | Transafricair | Callsign: Transafricair, | RWA | AVCODES |
| 6 | UR | Aerosun International, Inc. | ICAO: ASI, Callsign: Aerosun, Designator UR recalled by IATA. Name changed from Red Carpet Airlines in September 1981. | USA | AVCODES |
| 7 | UR | UTAir Express | ICAO: UTX, Callsign: UTAir-Express, IATA Prefix: 434, Ceased operations | RUS | AVCODES |
| 8 | UR | Uganda National Airlines Company Limited d/b/a/ Uganda Airlines | ICAO: UGD, Callsign: Crested, | EAU | AVCODES |
| 9 | URA | Aircompany Rosavia Ltd. | Callsign: Rosavia, | UA | AVCODES |
| 10 | URA | Aircompany Rosavia | | | ICAO1 |
| 11 | URBC | UGLY TRUCK / BEAUTIFUL SERVICE | | | SCAC4 |
| 12 | URBS | URBAN EXPRESS | | | SCAC4 |
| 13 | URC | United Railways Co. (Spokane, Portland & Seattle Ry.) | 7/1923-7/1936 | | NAKINA |
| 14 | URC | United Railways Co. | 4/1938-1/1941 | | NAKINA |
| 15 | URC | United Railways Co. | Apr-38 | | NRHS |
| 16 | URC | UNITED RAILWAYS CO. 9SPOKANE, PORTLAND & SEATTLE RWY.) | | | PWRC |
| 17 | URCS | UNITED RELOCATION SYSTEMS INC | | | SCAC4 |
| 18 | URCX | United Refining Co. | 8/1920-4/1970; eliminated 7/1971 | | NAKINA |
| 19 | URCX | United Refining Co. | 4/38-4/70 | | NRHS |
| 20 | URCX | UNITED REFINING CO. | | | PWRC |
| 21 | URDS | URS AUTO TRANSPORT DIVISION | | | SCAC4 |
| 22 | URDX | United States Steel Corp., Resource Development Group | added 10/1980; eliminated 4/1985 | | NAKINA |
| 23 | URDX | Arch of Kentucky, Inc. | added 4/1985; 1/1994; eliminated 4/1994; 7/2000-7/2005 (not listed) | | NAKINA |
| 24 | URDX | United States Steel Corp., Resource Development Group | added 10/80; eliminated 4/85 | | NRHS |
| 25 | URDX | Arch of Kentucky, Inc. | added 4/85; 1/94; eliminated 4/94; 7/2000 | | NRHS |
| 26 | URDX | ARCH OF KENTUCKY, INC. {UNITED STATES STEEL CORP., RESOURCE DEVELOPMENT GROUP] | | | PWRC |
| 27 | URDX | United States Steel | | | RSRV |
| 28 | URDX | ARCH OF KENTUCKY, INC. | | | SCAC4 |
| 29 | URE | Eureca srl | IATA: F4, Callsign: Eureca, Designator F4 recalled by IATA. Name changed from International Flying Services. ICAO designator changed from IFS | I | AVCODES |
| 30 | UREG | USCA REFRIGERATED | | | SCAC4 |
| 31 | URES | UNIVERSAL RELOCATION SYSTEMS INC | | | SCAC4 |
| 32 | UREU | URENCO LTD | | D | BIC |
| 33 | UREU | URENCO LTD | | | SCAC4 |
| 34 | URF | Executive Flight Services | Callsign: Executive Express, | M | AVCODES |
| 35 | URF | Surf Air | Callsign: Surfair, | USA | AVCODES |
| 36 | URFU | EUROTRANS LOGISTICS LLC | | RUS | BIC |
| 37 | URG | Air Urga | IATA: 3N, Callsign: Urga, IATA Prefix: 746, | UA | AVCODES |
| 38 | URG | Air Urga | IATA: 3N | | ICAO1 |
| 39 | URGX | UniCapital Rail Group | 7/2000 (not listed) | | NAKINA |
| 40 | URGX | UniCapital Rail Group | Jul-00 | | NRHS |
| 41 | URGX | UNICAPITAL RAIL GROUP | | | PWRC |
| 42 | URGY | URUGUAY TRUCKING | | | SCAC4 |
| 43 | URHC | UNIVERSAL ROAD HAUL CORP. | | | SCAC1 |
| 44 | URHS | United Railroad Historical Society of New Jersey | | USA | TRAFFIC |
| 45 | URHX | UNITED RAILWAY HISTORICAL SOCIETIES OF NEW JERSEY | | | PWRC |
| 46 | URI | uSKY AIR | Callsign: Uri Air, | ROK | AVCODES |
| 47 | URIM | UR IMAGE INC | | | SCAC4 |
| 48 | URJ | Star Air Aviation (Private) Limited | IATA: 6S, Callsign: Starav, | PK | AVCODES |
| 49 | URJ | Star Air | | | ICAO1 |
| 50 | URK | Turkestan | Callsign: Djuma, | KZ | AVCODES |
| 51 | URLL | UNCLE RAYS LLC | | | SCAC4 |
| 52 | URLO | URSA LOGISTICS | | | SCAC4 |
| 53 | URMX | Union Refrigerator Transit Lines, a Division of the General American Transportation Corp. | 7/1965-10/1966 | | NAKINA |
| 54 | URMX | Union Refrigerator Transit Lines | eliminated 7/1967 | | NAKINA |
| 55 | URMX | Union Refrigerator Transit Lines, a Division of the General American Transportation Corp. | 7/65-10/66 | | NRHS |
| 56 | URMX | Union Refrigerator Transit Lines | eliminated 7/67 | | NRHS |
| 57 | URMX | *UNION REFRIGERATOR TRANSIT LINES, DIV. GENERAL AMERICAN TRANSPORTATION CORP. | | | PWRC |
| 58 | URMX | +UNITRAC RAILROAD MATERIALS INC. | | | PWRC |
| 59 | URMX | UNITRAC RAILROAD MATERIALS INCORPOR | | | SCAC4 |
| 60 | URN | Turan Air Airline Company | IATA: 3T, Callsign: Turan, IATA Prefix: 359, Ceased operations in 2013. | AZ | AVCODES |
| 61 | URN | Turan Air | IATA: 3T | | ICAO1 |
| 62 | URO | Euroair Transport Ltd. | IATA: EZ, Callsign: Euroair, | GB | AVCODES |
| 63 | URO | European Cargo Limited | IATA: PS, Callsign: Euro, IATA Prefix: 436, IATA designator changed to SE. | GB | AVCODES |
| 64 | URO | European Cargo Limited | IATA: SE, Callsign: Euro, IATA Prefix: 436, IATA designator changed from PS*. | GB | AVCODES |
| 65 | UROI | UNITED ROAD ONTARIO INC | | | SCAC4 |
| 66 | UROS | URO SYSTEMS LLC | | | SCAC4 |
| 67 | URP | ARP 410 Airlines | Callsign: Air-Arp, | UA | AVCODES |
| 68 | URP | ARP 410 Airlines | | | ICAO1 |
| 69 | URPL | ULTIMATE RECYCLED PLASTICS | | | SCAC4 |
| 70 | URQR | URQUHART, RAY V | | | SCAC4 |
| 71 | URR | Aurora Airlines | Callsign: Air Aurora, Founded in 2005. Ceased operations in 2009. | SLO | AVCODES |
| 72 | URR | Aurora Airlines | | | ICAO1 |
| 73 | URR | Union R.R. Co. (Pittsburgh, PA) | 1/1975-7/2005 | | NAKINA |
| 74 | URR | Union R.R. Co. (Pittsburgh, PA) | 1/75-7/2000 | | NRHS |
| 75 | URR | UNION RAILROAD CO. (PITTSBURGH, PA) | | | PWRC |
| 76 | URR | Union Railroad Pittsburgh | | | RSRV |
| 77 | URR | UNION RAILROAD COMPANY | | | SCAC4 |
| 78 | URR | Union R.R. Co. (Pittsburgh, PA) | | USA | TRAFFIC |
| 79 | URS | Air Company LLC Silk Road Cargo Business | IATA: S9, Callsign: Silk Cargo, IATA Prefix: 939, | UZ | AVCODES |
| 80 | URSA | URSA SHIPPING | | | SCAC4 |
| 81 | URSC | UNITED RAILWAY SUPPLY CO. | | | PWRC |
| 82 | URSM | URS SMS LLC | | | SCAC4 |
| 83 | URSO | URSO FUEL OIL CO | | | SCAC4 |
| 84 | URST | UNIE VAN REDDING-EN SLEEPDIENS TOWA | | | SCAC4 |
| 85 | URT | Avia-Urartu | Callsign: Urartu Air, | AM | AVCODES |
| 86 | URTA | UNITED RIM TRANSPORT INC | | | SCAC4 |
| 87 | URTB | URTRUCKBROKER | | | SCAC4 |
| 88 | URTC | Union Refrigerator Transit Lines | a Division of the General American Transportation Corp. | USA | TRAFFIC |
| 89 | URTCo. | Union Refrigerator Transit Co. | 7/1935 | | NAKINA |
| 90 | URTS | URTRUCKSTUFF.COM LLC | | | SCAC4 |
| 91 | URTT | URUAMERICA TRUCKING LLC | | | SCAC4 |
| 92 | URTX | Union Refrigerator Transit Co. (previously U.R.T.Co.) | added 11/1934; 7/1935-4/1947 | | NAKINA |
| 93 | URTX | Union Refrigerator Transit Lines, a Division of the General American Transportation Corp. | 1/1950-4/1970; eliminated 10/1971 | | NAKINA |
| 94 | URTX | General American Transportation Corp., Freight Car Division | added 10/1971 | | NAKINA |
| 95 | URTX | General American Transportation Corp. | 1/1975-1/1980; eliminated 10/1992 | | NAKINA |
| 96 | URTX | Union Refrigerator Transit Lines, a Division of the General American Transportation Corp. | 4/38-4/70; eliminated 10/71 | | NRHS |
| 97 | URTX | General American Transportation Corp., Freight Car Division | added 10/71 | | NRHS |
| 98 | URTX | General American Transportation Corp. | 1/75-1/80; eliminated 10/92 | | NRHS |
| 99 | URTX | (GATX) RETIRED 08-19-92 ATP (1631) [UNION REFRIGERATOR TRANSIT LINES] | | | PWRC |
| 100 | URTX | Union Refrigerator Transit Lines (GATX) | | | RSRV |
