| 1 | XC | Air Caribbean | ICAO: CLT, Callsign: Caribbean, Ceased operations on 23 October 2002. | NA | AVCODES |
| 2 | XC | K.D. Air Corporation | ICAO: KDC, Callsign: Key Dee, Ceased operaitons. | CDN | AVCODES |
| 3 | XC | Action Airlines (Action Air Charter) | ICAO: AXQ, Callsign: Action Air, Designator XC recalled by IATA | USA | AVCODES |
| 4 | XC | Compania Radio Aeronautica Costarriceense, S.A. | | RCH | AVCODES |
| 5 | XC | Air Routing International Corp. | ICAO: ARC, | USA | AVCODES |
| 6 | XC | CrossCountry trains | | GB | TRAFFIC |
| 7 | XC | Cross Country Trains Ltd | | UK | VKM |
| 8 | XCA | Colt Transportes Aereos S.A. | Callsign: Colt, | BR | AVCODES |
| 9 | XCAD | XTRA CARTAGE AND DISTRIBUTION INC | | | SCAC4 |
| 10 | XCAG | XTREME CARGO INC | | | SCAC4 |
| 11 | XCC | Ecoturistica de Xcalac, S.A. de C.V. | Callsign: Xcalac, | MEX | AVCODES |
| 12 | XCC | Ecoturistica de Xcalak | | | ICAO1 |
| 13 | XCCU | QUZHOU XIECHENG CHEMICAL CO., LTD. | | PRC | BIC |
| 14 | XCCX | Xavier Chemical Co. | added 10/1999; 7/2000; eliminated 4/2002; 7/2005 (not listed) | | NAKINA |
| 15 | XCCX | Xavier Chemical Co. | added 10/99; 7/2000 | | NRHS |
| 16 | XCCX | XAVIER CHEMICAL CO. | | | PWRC |
| 17 | XCCX | Xavier Chemical Corporation | | | RSRV |
| 18 | XCEL | X-CEL X-RAY CORP | | | SCAC4 |
| 19 | XCFS | XCF SA DE CV | | | SCAC4 |
| 20 | XCH | Jet Exchange Limited | IATA: UH, Callsign: Exchange, | GB | AVCODES |
| 21 | XCHZ | XTRA INTERMODAL | | | SCAC4 |
| 22 | XCIC | XPRESS CONNECTIONS INC | | | SCAC4 |
| 23 | XCL | Contel ASC | | USA | AVCODES |
| 24 | XCL | Contel ASC | | | ICAO1 |
| 25 | XCLH | XOXXOX CHARTER BUS SERVICE INC | | | SCAC4 |
| 26 | XCLU | TEXTAINER SPECIAL EQUIP. LTD (SUBSID. OF TEXTAINER) | | | PWRC |
| 27 | XCLU | Textainer Special Equip. Limited | | | RSRV |
| 28 | XCLX | Xcel Energy | added 1/2006 | | NAKINA |
| 29 | XCLX | XCEL ENERGY | | | PWRC |
| 30 | XCLX | Xcel Energy | | | RSRV |
| 31 | XCLX | XCEL ENERGY | | | SCAC4 |
| 32 | XCN | U.S. Forest Service | Callsign: Fire Scan, ICAO designator changed from LDE. ICAO callsign changed from Fire Lead. | USA | AVCODES |
| 33 | XCO | Compuflight Operations Service, Inc. | | USA | AVCODES |
| 34 | XCO | Compuflight Operations Service | | | ICAO1 |
| 35 | XCPZ | XTRA INTERMODAL | | | SCAC4 |
| 36 | XCR | Miscellaneous Auxiliary Calegory | IATA: CR, Designator CR* recalled by IATA. Non-airline Org. in airline industry | USA | AVCODES |
| 37 | XCR | Miscellaneous Auxiliary Calegory | Designator CR* recalled by IATA. Non-airline Org. in airline industry | USA | AVCODES |
| 38 | XCS | Compuserve Incorporated | Non-airline Org. in airline industry | USA | AVCODES |
| 39 | XCS | Compuserve Incorporated | | | ICAO1 |
| 40 | XCSI | XPRESS COURIER SERVICES INC | | | SCAC4 |
| 41 | XCT | Aero Costa Taxi Aereo, S.A. de C.V. | Callsign: Aerocostaxi, | MEX | AVCODES |
| 42 | XCT | Aero Costa Taxi Aereo | | | ICAO1 |
| 43 | XCTA | CHICAGO TRANSIT AUTHORITY | | | PWRC |
| 44 | XCTG | XCELERATED TRANSPORTATION GROUP LLC | | | SCAC4 |
| 45 | XCTS | CLEVELAND TRANSIT SYSTEM | | | PWRC |
| 46 | XCTU | DIMC - DUBAI INTERNATIONAL MARINE CLUB | | UAE | BIC |
| 47 | XCTU | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 48 | XCTU | XTRA Intermodal (WPPA Ltd) | | | RSRV |
| 49 | XCTZ | XTRA INTERMODAL | | | PWRC |
| 50 | XCTZ | XTRA Intermodal | | | RSRV |
| 51 | XCTZ | XTRA INTERMODAL | | | SCAC4 |
| 52 | XCWZ | UNION PACIFIC [(XTRA) CHICAGO & NORTH WESTERN TRANS CO] | | | PWRC |
| 53 | XCWZ | Chicago & North Western (Union Pacific Railroad) | | | RSRV |
| 54 | XCWZ | UNION PACIFIC RAILROAD COMPANY | | | SCAC4 |
| 55 | XCX | Citibank, N.A. | Non-airline Org. in airline industry | USA | AVCODES |
| 56 | XCX | Citibank | | | ICAO1 |
