| 1 | XT | Air Exel Netherlands B.V. d/b/a KLM Exel | ICAO: AXL, Callsign: Exel Commuter, IATA Prefix: 824, Established on 26 April 1991. Commenced operations on 01 May 1991. | NL | AVCODES |
| 2 | XT | Sector Airlines | ICAO: XTR, Callsign: Exter, Designator recalled by IATA | CDN | AVCODES |
| 3 | XT | Servicos Auxiliares de Transportes Aereos (SATA) | | BR | AVCODES |
| 4 | XT | Air Exel Netherlands B.V. | ICAO: AXL, Callsign: Exel Commuter, IATA Prefix: 824, Name changed from Air Exel Netherlands B.V. d/b/a KLM Exel w.e.f. 06 November 2004. Ceased operations on 31 January 2005. | NL | AVCODES |
| 5 | XT | Skystar Airways Company Limited | | T | AVCODES |
| 6 | XT | PT. Indonesia AirAsia Extra | ICAO: IDX, Callsign: Red Phoenix, Ceased operations on 14 January 2019. Subsidary of AirAsia X Berhad. | RI | AVCODES |
| 7 | XT | Limited Liability Company GloBus | ICAO: CTU, Callsign: Citywings, | RUS | AVCODES |
| 8 | XT | X-Taget | Ostküstenbahn Gävle-Sundsvall/Ljusdal | S | TRAFFIC |
| 9 | XTA | Servicios Aereos Textra, S.A. de C.V. | Callsign: Textra, | MEX | AVCODES |
| 10 | XTA | Servicios Aereos Textra | | | ICAO1 |
| 11 | XTCH | XTC HEREFORD FARMS LTD | | | SCAC4 |
| 12 | XTCO | XS TRANSPORT CO | | | SCAC4 |
| 13 | XTCU | VAN DONGE EN DE ROO | | | PWRC |
| 14 | XTCU | Van Donge En De Roo | | | RSRV |
| 15 | XTCU | EXTRACONT LIMITED | | | SCAC4 |
| 16 | XTDS | XCEL TRUCK DELIVERY SERVICES | | | SCAC4 |
| 17 | XTEG | X-TREME ENERGY GROUP INC | | | SCAC4 |
| 18 | XTH | Xinjiang General Aviation Co., Ltd. | Callsign: Bright Pearl, | PRC | AVCODES |
| 19 | XTII | XTREME TRANSPORTATION I INC | | | SCAC4 |
| 20 | XTJ | Advance Aviation Services, Inc. | | USA | AVCODES |
| 21 | XTJ | Advance Aviation Services | | | ICAO1 |
| 22 | XTKL | XTREME TRUCKING LLC | | | SCAC4 |
| 23 | XTLD | XLINE TRANSPORT LTD | | | SCAC4 |
| 24 | XTLI | XTL INC | | | SCAC4 |
| 25 | XTLM | XAVIER TRANSPORT LIMITED LIABILITY | | | SCAC4 |
| 26 | XTLP | XTL TRANSPORTATION CORPORATION | | | SCAC4 |
| 27 | XTLT | XTL TRANSPORT INC | | | SCAC4 |
| 28 | XTME | XTREME CARTAGE AND WAREHOUSING SYST | | | SCAC4 |
| 29 | XTML | XTRA MILE TRANSPORT INC | | | SCAC4 |
| 30 | XTMM | XTREME TM | | | SCAC4 |
| 31 | XTMZ | (TMT) TRAILER MARINE TRANSPORT CORP. | | | PWRC |
| 32 | XTMZ | Trailer Marine Transport | | | RSRV |
| 33 | XTNL | XTER TRANSPORTATION LTD | | | SCAC4 |
| 34 | XTO | Express Tours | Callsign: Express Tours, | G | AVCODES |
| 35 | XTO | Express Tours | | | ICAO1 |
| 36 | XTOE | XTRA TWO ONE (21) | | | SCAC4 |
| 37 | XTR | Sector Airlines | Callsign: Exter, | CDN | AVCODES |
| 38 | XTR | Sector Airlines | IATA: XT, Callsign: Exter, Designator recalled by IATA | CDN | AVCODES |
| 39 | XTR | Sector Airlines | | | ICAO1 |
| 40 | XTR | XTR-SYSTEM DEVELOPMENT s.r.o | | CZ | VKM |
| 41 | XTRA | *FIRST UNION RAIL | | | PWRC |
| 42 | XTRA | *XTRA, INC. | | | PWRC |
| 43 | XTRA | XTRA INTERMODAL | | | SCAC4 |
| 44 | XTRC | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 45 | XTRC | XTERRA TRANSPORT CORP | | | SCAC4 |
| 46 | XTRF | XR TRANSPORT | | | SCAC4 |
| 47 | XTRI | X-TRUX INC | | | SCAC4 |
| 48 | XTRS | XPRESS TRAILER REPAIR & SERVICE INC | | | SCAC4 |
| 49 | XTRU | SEACO SRL | | BDS | BIC |
| 50 | XTRU | *GENSTAR CONTAINER CORPORATION | | | PWRC |
| 51 | XTRU | *ITEL CONTAINERS INTERNATIONAL CORPORATION | | | PWRC |
| 52 | XTRU | Genstar Container Corporation | | | RSRV |
| 53 | XTRU | GENSTAR CONTAINER CORPORATION | | | SCAC4 |
| 54 | XTRX | XTRA, Inc. | added 1/1980; 1/1980; eliminated 1/1990 | | NAKINA |
| 55 | XTRX | Chrysler Rail Transportation Corp. | added 1/1990; eliminated 4/1993 | | NAKINA |
| 56 | XTRX | U.S. Rail Services, Inc. | added 4/1993; 1/1994; eliminated 4/1994 | | NAKINA |
| 57 | XTRX | USL Capital Rail Services | added 4/1994; eliminated 10/1996 | | NAKINA |
| 58 | XTRX | First Union Rail | added 10/1996; 7/2000-7/2005 | | NAKINA |
| 59 | XTRX | XTRA, Inc. | added 1/80; 1/80; eliminated 1/90 | | NRHS |
| 60 | XTRX | Chrysler Rail Transportation Corp. | added 1/90; eliminated 4/93 | | NRHS |
| 61 | XTRX | U.S. Rail Services, Inc. | added 4/93; 1/94; eliminated 4/94 | | NRHS |
| 62 | XTRX | USL Capital Rail Services | added 4/94; eliminated 10/96 | | NRHS |
| 63 | XTRX | First Union Rail | added 10/96; 7/2000 | | NRHS |
| 64 | XTRX | FIRST UNION RAIL [(RUSX) USL CAPITAL RAIL SERVICES; CHRYSLER RAIL TRANSPORTATION CORP.; (XTRZ) XTRA INTERMODAL] | | | PWRC |
| 65 | XTRX | XTRA (First Union Rail) | | | RSRV |
| 66 | XTRZ | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 67 | XTRZ | XTRA Intermodal | | | RSRV |
| 68 | XTRZ | XTRA INTERMODAL | | | SCAC4 |
| 69 | XTTI | X-TREME TRANSPORT INC | | | SCAC4 |
| 70 | XTTX | Trailer Train Co. | added 4/1966 | | NAKINA |
| 71 | XTTX | Trailer Train Co. (FC flat cars equipped with hitches and bridge plates for the transportation of trailers. These cars have 4 hitches for handling 2 40-foot or 3 28-foot trailers) | 10/1966-10/1968 | | NAKINA |
| 72 | XTTX | Trailer Train Co. (flat cars, equipped with 4 hitches and bridge plates for the transportation of two trailers, 1 45' and 1 40' or 3 28' trailers) | 4/1970-7/1985 | | NAKINA |
| 73 | XTTX | TTX Co. (flat cars equipped with 4 collapsable hitches and bridge plates for the transportation of two trailers, 1-45' and 1-40' or 3-28' trailers) | 1/1992 | | NAKINA |
| 74 | XTTX | TTX Co. | 1/1994 | | NAKINA |
| 75 | XTTX | Trailer Train Co. | added 4/1966; 1/1975-1/1980; eliminated 1/1992 | | NAKINA |
| 76 | XTTX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 77 | XTTX | Trailer Train Co. | added 4/66 | | NRHS |
| 78 | XTTX | Trailer Train Co. (flat cars, equipped with 4 hitches and bridge plates for the transportation of two trailers, 1 45' and 1 40' or 3 28' trailers) | 1/75-1/80 | | NRHS |
| 79 | XTTX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 80 | XTTX | TTX Co. | added 1/92 | | NRHS |
| 81 | XTTX | Trailer Train Co. (FC flat cars equipped with hitches and bridge plates for the transportation of trailers. These cars have 4 hitches for handling 2 40-foot or 3 28-foot trailers) | 10/66-10/68 | | NRHS |
| 82 | XTTX | Trailer Train Co. | Apr-70 | | NRHS |
| 83 | XTTX | TTX Co. | Jan-94 | | NRHS |
| 84 | XTTX | TTX COMPANY (TRAILER TRAIN COMPANY) | | | PWRC |
| 85 | XTTX | Trailer Train (TTX Corporation) | | | RSRV |
| 86 | XTTX | TTX COMPANY | | | SCAC4 |
| 87 | XTWZ | (XTRZ) XTRA INTERMODAL | | | PWRC |
