| 1 | XSA | Spectrum Air Service, Inc. | | USA | AVCODES |
| 2 | XSA | Spectrum Air Service | | | ICAO1 |
| 3 | XSCZ | CSX TRANSPORTATION, INC. | | | PWRC |
| 4 | XSCZ | CSX Transportation | | | RSRV |
| 5 | XSEC | CITY TRANSIT DIVISION, SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (PHILADELPHIA) | | | PWRC |
| 6 | XSER | RED ARROW DIVISION, SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY | | | PWRC |
| 7 | XSER | XPEDITE TRANS SERVICES | | | SCAC4 |
| 8 | XSET | XSETRA INC | | | SCAC4 |
| 9 | XSFM | SAN FRANCISCO MUNICIPAL RWY (MUNI) | | | PWRC |
| 10 | XSHS | SHAKER HEIGHTS RAPID TRANSIT SYSTEM (CLEVELAND AREA) | | | PWRC |
| 11 | XSIC | XACT SYSTEMS INC | | | SCAC4 |
| 12 | XSIT | STATEN ISLAND RAPID TRANSIT OPERATING AUTHORITY (STATEN ISLAND RAILWAY) | | | PWRC |
| 13 | XSL | Sesatslab Proof-of-Concept Flights, Embry-Riddle University | Callsign: Satslab, Name changed from Southeast Satslab Consortium. | USA | AVCODES |
| 14 | XSL | Embry-Riddle Aeronautical University | | | ICAO1 |
| 15 | XSLL | X-SHIPPING L.L.C. | | | SCAC4 |
| 16 | XSLO | Express Slovakia | | SK | TRAFFIC |
| 17 | XSLZ | SOO LINE RAILROAD | | | PWRC |
| 18 | XSLZ | Soo Line Railroad (Canadian Pacific Railway) | | | RSRV |
| 19 | XSLZ | SOO LINE RAILROAD | | | SCAC4 |
| 20 | XSM | Steelman Aviation, Inc. t/a AirSmart | Callsign: Airsmart, ICAO designator changed from GDS. ICAO Callsign changed from Goldstrike. | USA | AVCODES |
| 21 | XSN | Stephenville Aviation Services | | CDN | AVCODES |
| 22 | XSN | AirSF Flight Service | Callsign: Santana, | USA | AVCODES |
| 23 | XSN | Stephenville Aviation Services | | | ICAO1 |
| 24 | XSOH | X'S & OH'S | | | SCAC4 |
| 25 | XSPD | XSPEEDIE | | | SCAC4 |
| 26 | XSPT | SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (SEPTA) | | | PWRC |
| 27 | XSPZ | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 28 | XSR | EAC Aircraft Management Corp | Callsign: Excutive Airshare, Name changed to Executive Flight Services, Inc. | USA | AVCODES |
| 29 | XSR | Executive Flight Services, Inc. | Callsign: Excutive Airshare, Name changed from EAC Aircraft Management Corp | USA | AVCODES |
| 30 | XSRF | X SIX | | | SCAC4 |
| 31 | XSRZ | (XTRZ) RETIRED 04-28-94 ATP | | | PWRC |
| 32 | XSS | Aero Express Intercontinental, S.A. de C.V. | Callsign: Inter Express, | MEX | AVCODES |
| 33 | XSS | Aero Express Intercontinental | | | ICAO1 |
| 34 | XST | Skyteam GmbH | Callsign: Skyteam, | D | AVCODES |
| 35 | XSTP | XSTREAM CONTAINER TRANSPORT INC | | | SCAC4 |
| 36 | XSTR | Xstrata Rail | | AUS | TRAFFIC |
| 37 | XSWZ | (XTRZ) RETIRED 04-28-94 ATP | | | PWRC |
