| 101 | XBO | Baseops International | | | ICAO1 |
| 102 | XBTK | X BORDER TRUCKING | | | SCAC4 |
| 103 | XC | Air Caribbean | ICAO: CLT, Callsign: Caribbean, Ceased operations on 23 October 2002. | NA | AVCODES |
| 104 | XC | K.D. Air Corporation | ICAO: KDC, Callsign: Key Dee, Ceased operaitons. | CDN | AVCODES |
| 105 | XC | Action Airlines (Action Air Charter) | ICAO: AXQ, Callsign: Action Air, Designator XC recalled by IATA | USA | AVCODES |
| 106 | XC | Compania Radio Aeronautica Costarriceense, S.A. | | RCH | AVCODES |
| 107 | XC | Air Routing International Corp. | ICAO: ARC, | USA | AVCODES |
| 108 | XC | CrossCountry trains | | GB | TRAFFIC |
| 109 | XC | Cross Country Trains Ltd | | UK | VKM |
| 110 | XCA | Colt Transportes Aereos S.A. | Callsign: Colt, | BR | AVCODES |
| 111 | XCAD | XTRA CARTAGE AND DISTRIBUTION INC | | | SCAC4 |
| 112 | XCAG | XTREME CARGO INC | | | SCAC4 |
| 113 | XCC | Ecoturistica de Xcalac, S.A. de C.V. | Callsign: Xcalac, | MEX | AVCODES |
| 114 | XCC | Ecoturistica de Xcalak | | | ICAO1 |
| 115 | XCCU | QUZHOU XIECHENG CHEMICAL CO., LTD. | | PRC | BIC |
| 116 | XCCX | Xavier Chemical Co. | added 10/1999; 7/2000; eliminated 4/2002; 7/2005 (not listed) | | NAKINA |
| 117 | XCCX | Xavier Chemical Co. | added 10/99; 7/2000 | | NRHS |
| 118 | XCCX | XAVIER CHEMICAL CO. | | | PWRC |
| 119 | XCCX | Xavier Chemical Corporation | | | RSRV |
| 120 | XCEL | X-CEL X-RAY CORP | | | SCAC4 |
| 121 | XCFS | XCF SA DE CV | | | SCAC4 |
| 122 | XCH | Jet Exchange Limited | IATA: UH, Callsign: Exchange, | GB | AVCODES |
| 123 | XCHZ | XTRA INTERMODAL | | | SCAC4 |
| 124 | XCIC | XPRESS CONNECTIONS INC | | | SCAC4 |
| 125 | XCL | Contel ASC | | USA | AVCODES |
| 126 | XCL | Contel ASC | | | ICAO1 |
| 127 | XCLH | XOXXOX CHARTER BUS SERVICE INC | | | SCAC4 |
| 128 | XCLU | TEXTAINER SPECIAL EQUIP. LTD (SUBSID. OF TEXTAINER) | | | PWRC |
| 129 | XCLU | Textainer Special Equip. Limited | | | RSRV |
| 130 | XCLX | Xcel Energy | added 1/2006 | | NAKINA |
| 131 | XCLX | XCEL ENERGY | | | PWRC |
| 132 | XCLX | Xcel Energy | | | RSRV |
| 133 | XCLX | XCEL ENERGY | | | SCAC4 |
| 134 | XCN | U.S. Forest Service | Callsign: Fire Scan, ICAO designator changed from LDE. ICAO callsign changed from Fire Lead. | USA | AVCODES |
| 135 | XCO | Compuflight Operations Service, Inc. | | USA | AVCODES |
| 136 | XCO | Compuflight Operations Service | | | ICAO1 |
| 137 | XCPZ | XTRA INTERMODAL | | | SCAC4 |
| 138 | XCR | Miscellaneous Auxiliary Calegory | IATA: CR, Designator CR* recalled by IATA. Non-airline Org. in airline industry | USA | AVCODES |
| 139 | XCR | Miscellaneous Auxiliary Calegory | Designator CR* recalled by IATA. Non-airline Org. in airline industry | USA | AVCODES |
| 140 | XCS | Compuserve Incorporated | Non-airline Org. in airline industry | USA | AVCODES |
| 141 | XCS | Compuserve Incorporated | | | ICAO1 |
| 142 | XCSI | XPRESS COURIER SERVICES INC | | | SCAC4 |
| 143 | XCT | Aero Costa Taxi Aereo, S.A. de C.V. | Callsign: Aerocostaxi, | MEX | AVCODES |
| 144 | XCT | Aero Costa Taxi Aereo | | | ICAO1 |
| 145 | XCTA | CHICAGO TRANSIT AUTHORITY | | | PWRC |
| 146 | XCTG | XCELERATED TRANSPORTATION GROUP LLC | | | SCAC4 |
| 147 | XCTS | CLEVELAND TRANSIT SYSTEM | | | PWRC |
| 148 | XCTU | DIMC - DUBAI INTERNATIONAL MARINE CLUB | | UAE | BIC |
| 149 | XCTU | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 150 | XCTU | XTRA Intermodal (WPPA Ltd) | | | RSRV |
| 151 | XCTZ | XTRA INTERMODAL | | | PWRC |
| 152 | XCTZ | XTRA Intermodal | | | RSRV |
| 153 | XCTZ | XTRA INTERMODAL | | | SCAC4 |
| 154 | XCWZ | UNION PACIFIC [(XTRA) CHICAGO & NORTH WESTERN TRANS CO] | | | PWRC |
| 155 | XCWZ | Chicago & North Western (Union Pacific Railroad) | | | RSRV |
| 156 | XCWZ | UNION PACIFIC RAILROAD COMPANY | | | SCAC4 |
| 157 | XCX | Citibank, N.A. | Non-airline Org. in airline industry | USA | AVCODES |
| 158 | XCX | Citibank | | | ICAO1 |
| 159 | XD | OAG Worldwide. | ICAO: XXD, Name changed from Offical Airline Guides (OAG). Non-airline org. relating to the airline industry | USA | AVCODES |
| 160 | XD | Air Transport Association of America (ATA) | ICAO: ATA, Non-airline org. relating to the airline industry | USA | AVCODES |
| 161 | XD | Universal Air Travel Plan (UATP) | ICAO: ATA, Non-airline org. relating ti the airline industry | USA | AVCODES |
| 162 | XD | Offical Airline Guides (OAG) | ICAO: XXD, Name changed to OAG Worldwide. Non-airline org. relating to the airline industry | USA | AVCODES |
| 163 | XD | Scheduled Airlines Traffic Offices, Inc. | Non-airline org. relating to the airline industry | USA | AVCODES |
| 164 | XDA | Bureau Veritas, S.A. | | F | AVCODES |
| 165 | XDA | Bureau Veritas | | | ICAO1 |
| 166 | XDD | Lockheed Duats | | USA | AVCODES |
| 167 | XDD | Lockheed DUATS | | | ICAO1 |
| 168 | XDEC | X D EXPRESS CORP | | | SCAC4 |
| 169 | XDEL1 | NS | | USA | TRAFFIC |
| 170 | XDGL | XENIOS DUTCH GROWERS LIMITED | | | SCAC4 |
| 171 | XDIR | XPRESS DIRECT (DIV OF U S XPRESS IN | | | SCAC4 |
| 172 | XDIT | EXPEDITE IT LLC | | | SCAC4 |
| 173 | XDS | Dispatch Services, Inc. | Non-airline Org. in airline industry | USA | AVCODES |
| 174 | XDS | Dispatch Services | | | ICAO1 |
| 175 | XDT | Date Transformation Corp. | | USA | AVCODES |
| 176 | XDT | Date Transformation Corp | | | ICAO1 |
| 177 | XDTZ | (XTRZ) RETIRED 10-19-93 ATP | | | PWRC |
| 178 | XDY | Dynair Services, Inc. | | USA | AVCODES |
| 179 | XDY | Dynair Services | | | ICAO1 |
| 180 | XE | SBS Aircraft | ICAO: ALT, Callsign: Green-Craft, | KZ | AVCODES |
| 181 | XE | Korea Express Air Co., Ltd. | ICAO: KEA, Callsign: Korea Express, IATA designator changed to KW. | ROK | AVCODES |
| 182 | XE | South Central Air, Inc. | ICAO: SCA, Designator recalled by IATA | USA | AVCODES |
| 183 | XE | Eurocontrol | ICAO: EUC, Designator XE recalled by IATA. Non-airline org. relating to the airline industry (ATC) | B | AVCODES |
| 184 | XE | Delux Public Charter, LLC d/b/a JetSuiteX | ICAO: JSX, Callsign: Bigstripe, Name cahnegd to Delux Public Charter, LLC d/b/a JSX Air | USA | AVCODES |
| 185 | XE | Delux Public Charter, LLC d/b/a JSX Air | ICAO: JSX, Callsign: Bigstripe, Name cahnegd from Delux Public Charter, LLC d/b/a JetSuiteX. | USA | AVCODES |
| 186 | XEC | International Executive Airlines Limited | Callsign: Airexec, | GB | AVCODES |
| 187 | XEC | Air Executive Charter GmbH | | D | AVCODES |
| 188 | XEC | Air Executive Charter | | | ICAO1 |
| 189 | XEJ | XE Jet Aviation Ltd | Callsign: Red Tail, | WAN | AVCODES |
| 190 | XEL | Helicopteros Xel-Ha, S.A. de C.V. | Callsign: Xel-ha, | MEX | AVCODES |
| 191 | XEL | Excel Charter Ltd. | Callsign: Heli Excel, | GB | AVCODES |
| 192 | XEL | Excel Charter | | | ICAO1 |
| 193 | XELP | EL PASO CITY LINES | | | PWRC |
| 194 | XEME | XTREME TRANSPORTATION INC | | | SCAC4 |
| 195 | XEN | Thro Aviation, Inc. d/b/a ZEN Flight | Callsign: Zen Jet, ICAO designator changed from THO. ICAO Callsign changed from Thro. | USA | AVCODES |
| 196 | XENF | XENONFS LLC | | | SCAC4 |
| 197 | XER | Xerox Corporation | Callsign: Xerox, | USA | AVCODES |
| 198 | XER | Xerox Corporation | | | ICAO1 |
| 199 | XES | Europstar Express | | M | AVCODES |
| 200 | XESI | XTEND ENERGY SERVICES INC | | | SCAC4 |
